Water Quality Control Commission
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WATER QUALITY CONTROL COMMISSION
5 CCR 1002-38
REGULATION NO. 38 CLASSIFICATIONS AND NUMERIC STANDARDS FOR SOUTH PLATTE RIVER BASIN, LARAMIE RIVER BASIN REPUBLICAN RIVER BASIN, SMOKY HILL RIVER BASIN
38.1 AUTHORITY
These regulations are promulgated pursuant to section 25-8-101 et seq C.R.S., as amended, and in partic ular, 25-8-203 and 25-8-204.
38.2 PURPOSE
These regulations establish classification and numeric standards for the South Platte River, the Laramie River, the Republican River and the Smoky Hill River, including all tributaries and standing bodies of wate r as indicated in section 38.6. The classifications identify the actual beneficial uses of the water. The nu meric standards are assigned to determine the allowable concentrations of various parameters. Discharg e permits will be issued by the Water Quality Control Division to comply with basic, narrative, and numeric standards and control regulations so that all discharges to waters of the state protect the classified uses. (See section 31.14). It is intended that these and all other stream classifications and numeric standards b e used in conjunction with and be an integral part of Regulation 31.0 - BASIC STANDARDS AND METHO DOLOGIES FOR SURFACE WATER.
38.3 INTRODUCTION
These regulations and Tables present the classifications and numeric standards assigned to stream segm ents listed in the attached Tables (See section 38.6). As additional stream segments are classified and n umeric standards for this drainage system are adopted, they will be added to or replace the numeric stand ards in the Tables in section 38.6. Any additions or revisions of classifications or numeric standards can be accomplished only after public hearing by the Commission and proper consideration of evidence and t estimony as specified by the statute and the “basic regulations”.
38.4 DEFINITIONS
See the Colorado Water Quality Control Act and the codified water quality regulations for definitions.
38.5 BASIC STANDARDS
(1) TEMPERATURE
All waters of the South Platte, Laramie, Republican and Smoky Hill River Basins are subject to th e following standard for temperature. (Discharges regulated by permits, which are within the per mit limitations, shall not be subject to enforcement proceedings under this standard.) Temperatur e shall maintain a normal pattern of diurnal and seasonal fluctuations with no abrupt changes and shall have no increase in temperature of a magnitude, rate, and duration deemed deleterious to t he resident aquatic life. This standard shall not be interpreted or applied in a manner inconsistent with section 25-8-104, C.R.S.
(2) QUALIFIERS
1 See Basic Standards and Methodologies for Surface Water for a listing of organic standards at 31. 11 and metal standards found at 31.16 Table III. The column in the tables headed “Water + Fish” are presumptively applied to all aquatic life class 1 streams which also have a water supply classi fication, and are applied to aquatic life class 2 streams which also have a water supply classificati on, on a case-by-case basis as shown in the Tables 38.6. The column in the tables at 31.11 hea ded “Fish Ingestion” is presumptively applied to all aquatic life class 1 streams which do not have a water supply classification, and are applied to aquatic life class 2 streams which do not have a water supply classification, on a case-by-case basis, as shown in the Tables in 38.6.
(3) URANIUM
(a) All waters of the South Platte River Basin are subject to the following basic standard for uranium, unless otherwise specified by a water quality standard applicable to a particular segment. However, discharges of uranium regulated by permits which are within these permit limitations shall not be a basis for enforcement proceedings under this basic standard.
(b) Uranium level in surface waters shall be maintained at the lowest practicable level.
(c) In no case shall uranium levels in waters assigned a water supply classification be increased by any cause attributable to municipal, industrial, or agricultural discharges so as to exceed 16.8-30 µg/l or naturally-occurring concentrations (as determined by the State of Colorado), whichever is greater.
(i) The first number in the 16.8-30 µg/l range is a strictly health-based value, based on the Commission’s established methodology for human health-based standards. The second number in the range is a maximum contaminant level, established under the federal Safe Drinking Water Act that has been determined to be an acceptable level of this chemical in public water supplies, taking treatability and laboratory detection limits into account. Control requirements, such as discharge permit effluent limitations, shall be established using the first number in the range as the ambient water quality target, provided that no effluent limitation shall require an “end-of-pipe” discharge level more restrictive than the second number in the range. Water bodies will be considered in attainment of this standard, and not included on the Section 303(d) List, so long as the existing ambient quality does not exceed the second number in the range.
(4) NUTRIENTS
Prior to May 31, 2022, interim nutrient values will be considered for adoption only in the limited cir cumstances defined at 31.17(e). These circumstances include headwaters, Direct Use Water Su pply (DUWS) Lakes and Reservoirs, and other special circumstances determined by the Commis sion. Additionally, prior to May 31, 2017, only total phosphorus and chlorophyll a will be consider ed for adoption. After May 31, 2017, total nitrogen will be considered for adoption per the circums tances outlined in 31.17(e).
Prior to May 31, 2022, nutrient criteria will be adopted for headwaters on a segment by segment b asis for the South Platte River Basin. Moreover, pursuant to 31.17(e), nutrient standards will only be adopted for waters upstream of all permitted domestic wastewater treatment facilities dischargi ng prior to May 31, 2012 or with preliminary effluent limits requested prior to May 31, 2012, and a ny non-domestic facilities subject to Regulation 85 effluent limits and discharging prior to May 31, 2012. The following is a list of all permitted domestic wastewater treatment facilities discharging p rior to May 31, 2012 or with preliminary effluent limits requested prior to May 31, 2012, and any n on-domestic facilities subject to Regulation 85 effluent limits and discharging prior to May 31, 201 2 in the South Platte River Basin:
2 Segment Permittee Facility name Permit No. COSPUS01a Alma Town of ALMA, TOWN OF CO0035769 FAIRPLAY SANITATION DISTRICT COSPUS01a Fairplay Sanitation District CO0040088 WWTF Boy Scouts of America Pikes COG58803 COSPUS01a CAMP ALEXANDER Peak Council 6 COSPUS02a Florissant Water and San Dist FLORISSANT WATER & SAN DIST CO0041416 TELLER COUNTY WW UTILITY COSPUS02a Teller County CO0044211 BOARD COSPUS03 Woodland Park City of WOODLAND PARK, CITY OF CO0043214 COSPUS03 YMCA Camp Shady Brook CAMP SHADY BROOK CO0045993 COG58812 COSPUS03 Lost Valley Ranch Corporation LOST VALLEY RANCH 2 COSPUS04 Will-O-Wisp Metro District WILL-O-WISP METRO DISTRICT CO0041521 COG58805 COSPUS04 Bailey WSD BAILEY WSD WWTF 6 COG58811 COSPUS04 Platte Canyon School Dist 1 PLATTE CANYON SCHOOL DIST 1 4 Mountain Water and Sanitation MOUNTAIN WATER & SAN COSPUS05c CO0022730 District DISTRICT Roxborough Water and ROXBOROUGH PARK WATER & COSPUS06a CO0041645 Sanitation District SAN WWTF Plum Creek Water Reclamation PLUM CREEK WW AUTHORITY COSPUS10a CO0038547 Authority WWTF Perry Park Water and COSPUS10a SAGEPORT WWTF CO0043044 Sanitation District Perry Park Water and COSPUS11b WAUCONDAH WWTP CO0022551 Sanitation District LITTLETON/ENGLEWOOD, CITIES COSPUS14 Littleton/Englewood Cities of CO0032999 OF Metro Waste Water METRO WASTEWATER RECLAM COSPUS15 CO0026638 Reclamation District DIST COSPUS15 Brighton City of BRIGHTON WWTF CO0021547 COSPUS15 South Adams County WSD WILLIAMS MONOCO WWTF CO0026662 Metro Waste Water COSPUS15 NORTHERN TREATMENT PLANT CO0048959 Reclamation District Ascentia Real Estate Holding FOXRIDGE FARMS MH COSPUS16c CO0028908 Company LLC COMMUNITY COG58907 COSPUS16c SouthWest Water Company HI-LAND ACRES W&SD WWTF 2 Mile High Racing and Enter dba COG58907 COSPUS16c ARAPAHOE PARK RACETRACK Arapahoe Park 3 COAL CREEK WW RECLAMATION COG58910 COSPUS16c Rangeview Metro District FAC 8 COSPUS16g Centennial Water and San Dist MARCY GULCH WWTF CO0037966 SAND CREEK WATER REUSE COSPUS16i Aurora City of - Aurora Water CO0026611 FACILTY Stonegate Village Metropolitan COSPCH01 STONEGATE VILLAGE WWTF CO0040291 District Pinery Water and Wastewater COSPCH01 PINERY WWTF CO0041092 District Parker Water and Sanitation COSPCH01 PARKER NORTH WRF CO0046507 District
3 Segment Permittee Facility name Permit No. Arapahoe County W and WW COSPCH04 LONE TREE CREEK WWTP CO0040681 Authority COSPBE01a Amen Real Estate LLC SINGIN' RIVER RANCH WWTF CO0035971 COSPBE01b Morrison Town of MORRISON TOWN OF CO0041432 Kittredge Sanitation and Water KITTREDGE SAN & WATER COSPBE01e CO0023841 District DISTRICT Bruce & Jayne Hungate DBA COSPBE01e BEAR CREEK CABINS CO0030856 Bear Creek Cabins EVERGREEN METROPOLITAN DIST COSPBE01e Evergreen Metropolitan District CO0031429 WWTF COSPBE04a Genesee WSD GENESEE WATER & SAN DISTRICT CO0022951 FOREST HILLS METROPOLITAN COSPBE04a Forest Hills Metro District CO0037044 DIST W. JEFFERSON COUNTY METRO COSPBE05 West Jefferson County MD CO0020915 DIST COSPBE05 Historic Brook Forest Inn LLC BROOK FOREST INN CO0030261 COSPBE06a Tiny Town Foundation Inc TINY TOWN CO0036129 Aspen Park Metropolitan ASPEN PARK METROPOLITAN COSPBE06a CO0000001 District DISTRICT Jefferson County Public CONIFER HIGH SCHOOL WW REC COSPBE06b CO0047988 Schools R-1 PLT Colorado Dept of EISENHOWER/JOHNSON COSPCL01 CO0026069 Transportation MEMORIAL TUNNELS COSPCL01 Clear Creek Skiing Corp LOVELAND SKI AREA WWTF CO0040835 COSPCL02a Georgetown Town of GEORGETOWN WWTF CO0027961 COG58805 COSPCL02c Central Clear Creek SD CENTRAL CLEAR CREEK SD WWTF 5 COG58806 COSPCL05 Empire Town of EMPIRE TOWN OF 5 COSPCL09a St Marys Glacier WSD ST. MARYS GLACIER WSD CO0023094 COSPCL10 Shwayder Camp Wastewater SHWAYDER CAMP WWTF CO0047473 COSPCL11 Idaho Springs City of IDAHO SPRINGS WWTF CO0041068 COSPCL12 Clear Creek WWTP CLEAR CREEK WWTP CO0046574 Black Hawk/Central City BLACK HAWK/CENTRAL CITY SD COSPCL13b CO0046761 Sanitation District WWTF COSPCL14a MillerCoors LLC MILLERCOORS GOLDEN FACILITY CO0001163 COSPBD01 Westminster City of BIG DRY CREEK WWTF CO0024171 COSPBD01 Broomfield City and County BROOMFIELD WWTF CO0026409 COSPBD01 Northglenn City of NORTHGLENN WWTF CO0036757 San Lazaro Park Properties COSPBO02b SAN LAZARO MHP WWTF CO0020184 LLP c/o BOULDER MOUNTAIN COSPBO02b BaseCamp Ventures LLC CO0040819 LODGEWWTF COG58811 COSPBO02b Mueller Red Lion Inn RED LION INN WWTF 8 COSPBO03 Nederland Town of NEDERLAND TOWN OF WWTF CO0020222 COSPBO04b Eldorado Springs Wastewater ELDORADO SPRINGS WWTF CO0047651
4 Segment Permittee Facility name Permit No. COG58810 COSPBO04b San Souci MHP SAN SOUCI MHP 1 COSPBO07b Louisville City of LOUISVILLE WWTF CO0023078 COSPBO07b Lafayette City of LAFAYETTE WWTF CO0023124 COSPBO07b Erie Town of ERIE WWTF CO0045926 Superior Metropolitan District SUPERIOR METROPOLITAN DIST COSPBO08 CO0043010 No 1 NO1 COSPBO09 Boulder City of 75TH ST WWTP CO0024147 ERIE NORTH WATER COSPBO10 Erie Town of CO0048445 RECLAMATION FACILITY B & B Mobile Home and RV COG58810 COSPBO10 B & B MOBILE HOME & RV PARK Park 7 COSPBO14 Lake Eldora WSD LAKE ELDORA WSD WWTF CO0020010 COSPSV02a Peaceful Valley Ranch LLC PEACEFUL VALLEY RANCH WWTF CO0048828 Seventh-Day Adventist Assoc COSPSV02a GLACIER VIEW RANCH CO0030112 of Colorado Aspen Lodge at Estes Park ASPEN LODGE AT ESTES PARK COSPSV02a CO0042820 Corp CORP COSPSV02b Lyons Town of LYONS TOWN OF CO0020877 COSPSV03 Longmont City of LONGMONT WWTF CO0026671 COSPSV03 St Vrain Sanitation District ST VRAIN SANITATION DISTRICT CO0041700 COSPSV06 Niwot Sanitation District NIWOT SANITATION DISTRICT CO0021695 LAKE THOMAS SUBDIVISION COSPSV06 Mead Town of CO0046868 WWTF COSPSV06 Mead Town of MEAD, TOWN OF CO0046876 COSPSV06 Fairways Metro Dist FAIRWAYS WWTF CO0048411 COSPMS01a Fort Lupton City of FORT LUPTON WWTF CO0021440 COSPMS01b Evans City of EVANS CITY OF WWTF CO0020508 COSPMS01b Kersey Town of KERSEY WWTF CO0021954 COSPMS01b Platteville Town of PLATTEVILLE WWTF CO0040355 COSPMS01b Evans City of HILL-N-PARK SANITATION DIST. CO0047287 COG58805 COSPMS01b La Salle Town of LA SALLE TOWN OF 8 COG58812 COSPMS01b Gilcrest Town of GILCREST WWTF 1 COG58903 COSPMS03a Elizabeth Town of GOLD CREEK 7 Galeton Water and Sanitation COSPMS03a GALETON WATER & SAN DISTRICT CO0043320 District COSPMS03a Orica USA Inc ORICA USA, INC. CO0046221 COSPMS03a Spring Valley Ranch SPRING VALLEY RANCH WWTF CO0046965 COSPMS03a Front Range Airport WWTF FRONT RANGE AIRPORT WWTF CO0047741 COSPMS04 Lochbuie Town of LOCHBUIE TOWN OF CO0047198 COSPMS05a Swift Beef Company SWIFT BEEF - LONE TREE CO0027707
5 Segment Permittee Facility name Permit No. COG58910 COSPMS05c Hudson WWTF HUDSON MECHANICAL WWTF 4 COSPMS06 Keenesburg Town of KEENESBURG TOWN OF CO0041254 COG58906 COSPMS06 Bennett Town of BENNETT TOWN OF 9 ESTES PARK SANITATION COSPBT02 Estes Park Sanitation District CO0020290 DISTRICT Upper Thompson Sanitation COSPBT02 UTSD WWTF CO0031844 District COSPBT04c Loveland City of LOVELAND WWTP CO0026701 COSPBT05 Milliken Town of MILLIKEN SANITATION DISTRICT CO0042528 COSPBT05 Johnstown Town of LOW POINT WWTP CO0047058 HIDDEN VIEW ESTATES HOA COSPBT07 Hidden View Estates HOA CO0048861 WWTF COSPBT09 Johnstown Town of JOHNSTOWN CENTRAL WWTF CO0021156 COSPBT09 Riverglen Homeowners Assoc RIVERGLEN HOA WWTF CO0029742 COSPBT09 Berthoud Town of BERTHOUD, TOWN OF CO0046663 COSPBT10 Berthoud Town of SERENITY RIDGE WWTF CO0047007 Western Mini-Ranch/Vaquero WESTERN MINI-RANCH/VAQUERO COG58909 COSPBT10 Estates Sewer Assoc. EST 5 Berthoud Estates Community COG58909 COSPBT10 BERTHOUD ESTATES WWTF Assoc 7 Fox Acres Community Services COG58911 COSPCP08 FOX ACRES WWTF Corp 2 COSPCP08 Girl Scouts of Colorado MAGIC SKY RANCH G.S. CAMP CO0047317 COSPCP11 Fort Collins City of MULBERRY WWTP CO0026425 COSPCP11 Fort Collins City of DRAKE WWTP CO0047627 COSPCP12 Windsor, Town of WINDSOR TOWN OF WWTF CO0020320 COSPCP12 Greeley City of GREELEY CITY OF CO0040258 LEPRINO GREELEY FACILITY COSPCP12 Leprino Foods Company CO0048860 WWTF COSPCP13a Anheuser Busch Inc NUTRI-TURF, INC. CO0039977 COSPCP13a Eaton Town of EATON, TOWN OF CO0047414 Saddler Ridge Metro Dist Water SADDLER RIDGE METRO DIST COG58910 COSPCP13a Reclamation Facility WATER RECLAMATION FACILITY 7 BOXELDER SANITATION DISTRICT COSPCP13b Boxelder Sanitation District CO0020478 WWTF COSPCP13b Wellington Town of WELLINGTON WWTF CO0046451 South Fort Collins Sanitation COSPCP22 SOUTH FORT COLLINS SAN DIST CO0020737 District COSPLS01 Western Sugar Cooperative FORT MORGAN FACILITY CO0041351 COSPLS01 Cargill Meat Solutions FORT MORGAN BEEF PLANT CO0044270 COSPLS01 Julesburg Town of JULESBURG TOWN OF CO0021113 COSPLS01 Brush City of BRUSH CITY OF CO0021245 COSPLS01 Sterling City of STERLING CITY OF CO0026247
6 Segment Permittee Facility name Permit No. COSPLS01 Fort Morgan City of FORT MORGAN CITY OF CO0044849 COG58801 COSPLS01 Snyder Sanitation District SNYDER SANITATION DISTRICT 6 MORGAN HEIGHTS COG58804 COSPLS01 Morgan Heights WSD WATER&SEWER INC 0 COG58810 COSPLS01 Ovid Town of OVID TOWN OF 6 COSPLS02a Leprino Foods Company FORT MORGAN CHEESE FACILITY CO0043958 COG58900 COSPLS02a Deer Trail Town of DEER TRAIL WWTF 2 COG58903 COSPLS02a Hillrose Town of HILLROSE WWTF 0 Byers Water and Sanitation BYERS WATER AND SANITATION COG58903 COSPLS02a District DISTRICT 3 Eastern Adams County Metro EASTERN ADAMS CO METRO DIST COG58903 COSPLS02a District WWTF 5 COSPLS02b Kiowa Town of KIOWA WWTF CO0033405 ELBERT WATER & SANITATION COG58906 COSPLS02b Elbert Water Sanitation District DIST WWTF 5 COSPRE03 Wray City of WRAY CITY OF CO0023833 COG58903 COSPRE06 Flagler Town of FLAGER WWTF 6 COG58905 COSPRE06 Arriba Town of ARRIBA WWTF 5 COG58905 COSPRE06 Holyoke City of HOLYOKE, CIY OF 9 COG58906 COSPRE06 Akron Town of AKRON WWTF 1 COG58906 COSPRE06 Haxtun Town of HAXTUN, TOWN OF 2 COG58910 COSPRE06 Stratton Town of STRATTON WWTF 0 COG58911 COSPRE06 Burlington City of BURLINGTON CITY OF WWTF 4 COG58912 COSPRE06 Seibert Town of SEIBERT WWTF 0 Cheyenne Wells Sanitation CHEYENNE WELLS SANITATION COG58903 COSPRE07 District No 1 DIST 9 COG58900 Unclassified Silco Oil Co TOMAHAWK TRUCK STOP 3 Prior to May 31, 2022: • For segments located entirely above these facilities, nutrient standards apply to the entire segment. • For segments with portions downstream of these facilities, nutrient standards only apply above these facilities. A footnote “C” was added to the total phosphorus and chlorophyll a standards in these segments. The footnote references the table of qualified facilities at 38.5(4). • For segments located entirely below these facilities, nutrient standards do not apply.
A footnote “B” was added to the total phosphorus and chlorophyll a standards in lakes segments as nutrients standards apply only to lakes and reservoirs larger than 25 acres surface area.
7 38.6 TABLES
(1) Introduction
The numeric standards for various parameters in the attached tables were assigned by the Com mission after a careful analysis of the data presented on actual stream conditions and on actual a nd potential water uses.
Numeric standards are not assigned for all parameters listed in the Tables attached to 31.0. If ad ditional numeric standards are found to be needed during future periodic reviews, they can be ass igned by following the proper hearing procedures.
(2) Abbreviations:
(a) The following abbreviations are used in the attached tables: ac = acute (1-day) Ag = Silver Al = Aluminum As = Arsenic B = Boron Ba = Barium Be = Beryllium oC = degrees celsius Cd = Cadmium ch = chronic (30-day) Chla = Chlorophyll a CL = cold lake temperature tier Cl = Chloride CLL = cold large lake temperature tier Cl2 = residual chlorine CN = free cyanide CrIII = trivalent chromium CrVI = hexavalent chromium CS-I = cold stream temperature tier one CS-II = cold stream temperature tier two Cu = Copper dis = Dissolved D.O. = Dissolved oxygen DM = daily maximum DUWS = direct use water supply E. coli = Eschericia coli F = Fluoride Fe = Iron Hg = Mercury mg/l = milligrams per liter ml = Milliliters Mn = Manganese Mo = molybdenum MWAT = maximum weekly average temperature NH3 = ammonia as N (nitrogen) Ni = Nickel NO2 = nitrite as N (nitrogen) NO3 = nitrate as N (nitrogen) OW = outstanding waters
8 P = Phosphorus Pb = Lead S = sulfide as undissociated H2S (hydrogen sulfide) Sb = Antimony Se = Selenium SO4 = Sulfate sp = Spawning T = temperature Tl = Thallium Tot = total Tr = Trout Trec = total recoverable TVS = table value standard U = Uranium µg/l = micrograms per liter UP = use-protected WAT = weekly average temperature WL = warm lake temperature tier WS = water supply WS-I = warm stream temperature tier one WS-II = warm stream temperature tier two WS-III = warm stream temperature tier three Zn = Zinc
(b) In addition, the following abbreviations are used:
Fe(ch) = WS(dis) Mn(ch) = WS(dis) SO4 = WS
These abbreviations mean: For all surface waters with an actual water supply use, the le ss restrictive of the following two options shall apply as numerical standards, as specified in the Basic Standards and Methodologies at 31.11(6);
(i) existing quality as of January 1, 2000; or
(ii) Iron = 300 µg/l (dissolved) Manganese = 50 µg/l (dissolved) SO4 = 250 mg/l
For all surface waters with a “water supply” classification that are not in actual use as a w ater supply, no water supply standards are applied for iron, manganese or sulfate, unless the Commission determines as the result of a site-specific rulemaking hearing that such s tandards are appropriate.
(c) As used in the Temporary Modifications and Qualifiers column of the Tables, the term “type A” refers to a Temporary Modification adopted pursuant to subsection 31.7(3)(a)(ii) (A) of the Basic Standards and Methodologies for Surface Water (i.e., “there is significant uncertainty regarding the water quality standard necessary to protect current and/or future use”). As used in the Temporary Modifications and Qualifiers column of the Tables, the term “type B” refers to a Temporary Modification adopted pursuant to subsection 31.7(3)(a)(ii)(B) of the Basic Standards and Methodologies for Surface Water (i.e., “there is significant uncertainty regarding the extent to which existing quality is the result of natural or irreversible human-induced conditions”).
(d) Temporary Modification for Water + Fish Chronic Arsenic Standard
9 (i) The temporary modification for chronic arsenic standards applied to segments with an arsenic standard of 0.02 µg/l that has been set to protect the Water+Fish qualifier is listed in the temporary modification and qualifiers column as As(ch)=hybrid.
(ii) For discharges existing on or before 6/1/2013, the temporary modification is: As(ch)=current condition, expiring on 12/31/2021.
(iii) For new or increased discharges commencing on or after 6/1/2013, the temporary modification is: As(ch)=0.02-3.0 µg/l (Trec), expiring on 12/31/2021. (a) The first number in the range is the health-based water quality standard previously adopted by the Commission for the segment. (b) The second number in the range is a technology based value established by the Commission for the purpose of this temporary modification. (c) Control requirements, such as discharge permit effluent limitations, shall be established using the first number in the range as the ambient water quality target, provided that no effluent limitation shall require an “end-of- pipe” discharge level more restrictive than the second number in the range.
(3) Table Value Standards
In certain instances in the attached tables, the designation “TVS” is used to indicate that for a part icular parameter a “table value standard” has been adopted. This designation refers to numerical criteria set forth in the Basic Standards and Methodologies for Surface Water. The criteria for whi ch the TVS are applicable are on the following table.
TABLE VALUE STANDARDS (Concentrations in µg/l unless noted)
PARAMETER(1) TABLE VALUE STANDARDS (2)(3) Aluminum (1.3695[ln(hardness)]+1.8308) (Trec) Acute = e
pH equal to or greater than 7.0
Chronic=e(1.3695[ln(hardness)]-0.1158)
pH less than 7.0
Chronic= e(1.3695[ln(hardness)]-0.1158) or 87, whichever is more stringent Ammonia (4) Cold Water = (mg/l as N)Total 0.275 39.0 acute 7.204 pH pH 7.204 1 10 1 10
0.0577 2.487 0.028(25T ) MIN 2.85, 1.45 10 chronic 7.688 pH pH 7.688 1 10 1 10 Warm Water = (mg/l as N)Total
0.411 58.4 acute 7.204 pH pH 7.204 1 10 1 10
10 0.0577 2.487 0.028(25T ) chronic ( Apr1 Aug 31) MIN 2.85, 1.45 10 7.688 pH pH 7.688 1 10 1 10
0.0577 2.487 0.02825MAX T , 7 chronic (Sep1 Mar 31) 1.45 10 7.688 pH pH 7.688 1 10 1 10
Acute = (1.136672-[ln(hardness) x (0.041838)])*e(0.9151[ln(hardness)]-3.1485) Cadmium Acute(Trout) = (1.136672-[ln(hardness) x (0.041838)])*e(0.9151[ln(hardness)]-3.6236) Chronic = (1.101672-[ln(hardness) x (0.041838)])*e(0.7998[ln(hardness)]-4.4451)
Chromium III(5) Acute = e(0.819[ln(hardness)]+2.5736)
Chronic = e(0.819[ln(hardness)]+0.5340)
Chromium VI(5) Acute = 16
Chronic = 11
Copper Acute = e(0.9422[ln(hardness)]-1.7408)
Chronic = e(0.8545[ln(hardness)]-1.7428)
Lead Acute = (1.46203-[ln(hardness)*(0.145712)])*e(1.273[ln(hardness)]-1.46)
Chronic = (1.46203-[(ln hardness)* (0.145712)])*e(1.273[ln(hardness)]-4.705)
Manganese Acute= e(0.3331[ln(hardness)]+6.4676)
Chronic= e(0.3331[ln(hardness)]+5.8743)
Nickel Acute = e(0.846[ln(hardness)]+2.253)
Chronic = e(0.846[ln(hardness)]+0.0554)
Selenium(6) Acute = 18.4
Chronic = 4.6
Silver Acute = ½ e(1.72[ln(hardness)]-6.52)
Chronic = e(1.72[ln(hardness)]-9.06)
Chronic(Trout) = e(1.72[ln(hardness)]-10.51) TEMPERATURE TIER SPECIES EXPECTED APPLICABLE TEMPERATURE Temperature TIER CODE TO BE PRESENT MONTHS STANDARD (OC) (MWAT) (DM) Cold Stream CS-I brook trout, cutthroat trout Tier I June – Sept. 17.0 21.7 Oct. - May 9.0 13.0 Cold Stream CS-II all other cold-water species April – Oct. 18.3 23.9
11 Tier II Nov. - March 9.0 13.0 Cold Lake CL brook trout, brown trout, cutthroat trout, lake trout, April – Dec. 17.0 21.2 rainbow trout, Arctic grayling, sockeye salmon Jan. - March 9.0 13.0 brown trout, lake trout, Temperature Cold Large CLL April – Dec. 18.3 23.8 Lake (>100 rainbow trout acres surface area) Jan. - March 9.0 13.0 Warm Stream WS-I common shiner, Johnny Tier I darter, orangethroat darter March – Nov. 24.2 29.0 Dec. – Feb. 12.1 14.5 Warm Stream WS-II brook stickleback, central stoneroller, creek chub, March – Nov. 27.5 28.6 Tier II longnose dace, Northern redbelly dace, finescale dace,razorback sucker, white sucker Dec. – Feb. 13.8 14.3 Warm Stream WS-III all other warm-water species Tier III March – Nov. 28.7 31.8 Dec. – Feb. 14.3 15.9 Yellow perch, walleye, pumpkinseed, smallmouth Warm Lakes WL bass, striped bass, white April – Dec. 26.3 29.5 bass, largemouth bass, bluegill, spottail shiner, Jan. - March Northern pike, tiger 13.2 14.8 muskellunge, black crappie, common carp, gizzard shad, sauger, white crappie, wiper
Uranium Acute = e(1.1021[ln(hardness)]+2.7088)
Chronic = e(1.1021[ln(hardness)]+2.2382)
Zinc Acute = 0.978*e (0.9094[ln(hardness)]+0.9095)
Chronic = 0.986*e (0.9094[ln(hardness)]+0.6235)
TABLE VALUE STANDARDS - FOOTNOTES
(1) Metals are stated as dissolved unless otherwise specified.
(2) Hardness values to be used in equations are in mg/l as calcium carbonate and shall be no greater than 400 mg/L except for aluminum for which hardness shall be no greater than 220 mg/L. The hardness values used in calculating the appropriate metal standard should be based on the lower 95 per cent confidence limit of the mean hardness value at the periodic low flow criteria as determined from a regression analysis of site-specific data. Where insufficient site-specific data exists to define the mean hardness value at the periodic low flow criteria, representative regional data shall be used to perform the regression analysis. Where a regression analysis is not appropriate, a site-specific method should be used. In calculating a hardness value, regression analyses should not be extrapolated past the point that data exist.
(3) Both acute and chronic numbers adopted as stream standards are levels not to be exceeded more than once every three years on the average.
(4) For acute conditions the default assumption is that salmonids could be present in cold water segments and should be protected, and that salmonids do not need to be protected in warm water segments. For chronic conditions, the default assumptions are that early life stages could be present all year in cold water segments and should be protected. In warm water segments the default assumption is that early life stages are present and should be protected only from April 1
12 through August 31. These assumptions can be modified by the Commission on a site-specific basis where appropriate evidence is submitted.
(5) Unless the stability of the chromium valence state in receiving waters can be clearly demonstrated, the standard for chromium should be in terms of chromium VI. In no case can the sum of the instream levels of Hexavalent and Trivalent Chromium exceed the water supply standard of 50 µg/l total chromium in those waters classified for domestic water use.
(6) Selenium is a bioaccumulative metal and subject to a range of toxicity values depending upon numerous site-specific variables.
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(4) Assessment Criteria
The following criteria shall be used when assessing whether a specified waterbody is in attainme nt of the specified standard.
(a) Upper South Platte Segment 6b, Chatfield Reservoir: Assessment Thresholds
chlorophyll = 11.2 µg/l, summer average, 1 in 5 year allowable exceedance frequency phosphorus(Tot) = 0.035 mg/l, summer average, 1 in 5 year allowable exceedance frequ ency.
(b) Upper South Platte Segment 16h: Selenium Assessment Locations ● Toll Gate Creek (TG6): Downstream of the confluence of East and West Toll Gate Creeks, at 6th Avenue near the gage station. ● East Toll Gate Creek (ET1): Upstream of the confluence with West Toll Gate Creek, at Chambers Road and 1st Avenue. ● West Toll Gate Creek (WT1): Upstream of the confluence with East Toll Gate Creek, at 2nd Avenue.
(c) Upper South Platte Segment 15 and Middle South Platte Segment 1a: Dissolved Oxygen Assessment Locations
For the purpose of determining attainment of the standard, dissolved oxygen measureme nts shall only be taken in the flowing portion of the stream and at mid depth, and at least six inches above the bottom of the channel. Dissolved oxygen measurements in man-ma de pools are not to be used for determination of attainment of the standards.
(d) Big Dry Creek Segment 1: Selenium Assessment Locations ● bdc 1.5: Upstream of Broomfield Wastewater Treatment Plant ● bdc 2.0: Upstream of Westminster Big Dry Creek Wastewater Treatment Facility ● bdc 4.5: Upstream of Northglenn Wastewater Treatment Plant
(e) Big Dry Creek Segment 2 (Standley Lake): Assessment Thresholds
Chlorophyll = 4.4 µg/L, Mar-Nov average, 1 in 5 yr allowable exceedance frequency
(f) Upper South Platte Segment 16i, Sand Creek from Toll Gate Creek to the confluence with the South Platte River: assessment locations for selenium and total mercury.
Selenium Assessment Locations:
13 ● Upper – (SWA): Downstream of the confluence of Sand Creek and Toll Gate Creek approximately 250 meters upstream of the Sand Creek Water Reuse Facility (SCWRF) discharge near the Peoria Street Bridge. ● Lower – (SW1): Above Suncor, approximately 60 meters upstream of the Union Pacific Railroad crossing and upstream of Brighton Boulevard.
Mercury Assessment Locations and Method: ● Sand Creek (SWP) – Downstream of the sheet piling drop structure located near the Brighton Blvd. Bridge. ● Sand Creek (SWP2-1) – Approximately 600 feet downstream of Suncor Outfall 003 and immediately upstream of the Burlington Ditch Siphon. ● Attainment of the standard below Brighton Blvd. shall be assessed using the weighted 85th percentile total mercury concentration from both assessment locations.
(g) Upper South Platte Segment 16g (Marcy Gulch): Selenium assessment.
Determination of attainment of the chronic and acute selenium standards will be based o n the 85th and 95th percentile, respectively, of paired samples taken the same day from fro m the two following locations:
● L29: Marcy Gulch upstream of Santa Fe Drive, immediately upstream of the Centennial Water & Sanitation District WWTF
● L36: Marcy Gulch upstream of the confluence with the South Platte River.
(h) Upper South Platte Segment 16j: Selenium assessment. Determination of attainment of the chronic and acute selenium standards will be based o n the 85th and 95th percentile, respectively. The selenium assessment locations are: ● Lee Gulch: Upstream of the confluence with the South Platte River ● Little’s Creek: Upstream of the confluence with the South Platte River ● Big Dry Creek: Upstream of the confluence with the South Platte River ● Little Dry Creek: Upstream of the confluence with the South Platte River
(i) Cherry Creek Segment 4b: Selenium assessment
Determination of attainment of the chronic and acute selenium standards will be based o n the 85th and 95th percentile, respectively.
● Upper Cottonwood Creek: From headwaters to confluence with Lone Tree Creek, to be assessed at CT-P2 — 39.605694, -104.84825. At Peoria St.
● Lower Cottonwood Creek: From confluence with Lone Tree Creek to terminus at Cherry Creek Reservoir, to be assessed at CT2-39.627861, -104.85025. West of Perimeter Road and south of bike path.
● Upper Lone Tree Creek: From headwaters to just above site LTC-3, to be assessed using data from LTC-1 and LTC-2 LTC-1 — 39.58435, -104.838017. Approximately 0.15 miles N of S. Revere Pkwy.
14 LTC-2 — 39.59685, -104.838217. Approximately 10 yards N of E. Peakview Ave.
● Lower Lone Tree Creek: From site LTC-3 to confluence with Cottonwood Creek, to be assessed using data from LTC-3 and LTC-4 LTC-3 — 39.604817, - 104.837083. Below ACWWA Lone Tree facility outfall. LTC-4 — 39.614483, 104.840217. Downstream of confluence with Windmill Creek
● Upper Windmill Creek: From Headwaters to WC-1 — Site WC-1-39.574967, -104.830017. West of Potomac St and South of Broncos Pkwy.
● Middle Windmill Creek: All sites between (but not including) WC-1 and WC-2. WC-1—39.574967, -104.830017. West of Potomac St and South of Broncos Pkwy. WC-2—39.59655, -104.821767. North of Cherry Creek Trail.
● Lower Windmill Creek: From site WC-2 to confluence with Lone Tree Creek, to be assessed at WC-2-39.59655, -104.821767. North of Cherry Creek Trail.
(j) Clear Creek Segment 5: Manganese assessment
● Below Woods Creek: West Fork of Clear Creek approximately 0.3 miles downstream of Berthoud Falls (39.771829°, -105.803418°).
● Mouth of West Fork: West Fork of Clear Creek near County Road 257.
38.7 COMMISSION’S DETERMINATION REGARDING STATE WATERS
(1) Introduction
The following list describes the Commission’s determinations regarding water bodies that do not contain “State Waters.”
(2) Determinations
(a) Marston Forebay located in Upper South Platte Segment 23 within Sections 11, 12, 13 and 14 in Township 5 South, Range 69 West of the 6th P.M. in the City and County of Denver, Colorado.
[INSERT TABLES]
15 STREAM CLASSIFICATIONS and WATER QUALITY STANDARDS – FOOTNOTES
(A) Whenever a range of standards is listed and referenced to this footnote, the first number in the range is a strictly health-based value, based on the Commission’s established methodology for human health-based standards. The second number in the range is a maximum contaminant level, established under the federal Safe Drinking Water Act that has been determined to be an acceptable level of this chemical in public water supplies, taking treatability and laboratory detection limits into account. Control requirements, such as discharge permit effluent limitations, shall be established using the first number in the range as the ambient water quality target, provided that no effluent limitation shall require an “end-of-pipe” discharge level more restrictive than the second number in the range. Water bodies will be considered in attainment of this standard, and not included on the Section 303(d) List, so long as the existing ambient quality does not exceed the second number in the range.
(B) Total phosphorus (TP) and chlorophyll a standards apply only to lakes and reservoirs larger than 25 acres surface area.
(C) Total phosphorus and chlorophyll a standards apply only above the facilities listed at 38.5(4).
(D) Assessment of adequate refuge shall rely on the Cold Large Lake table value temperature criterion and applicable dissolved oxygen standard rather than the site-specific temperature standard.
66 38.90 STATEMENT OF BASIS, SPECIFIC STATUTORY AUTHORITY AND PURPOSE; JUNE 9, 2015 RULEMAKING; FINAL ACTION AUGUST, 2014; EFFECTIVE DATE DECEMBER 31, 2015
The provisions of C.R.S. 25-8-202(1)(a), (b) and (2); 25-8-203; 25-8-204; and 25-8-402; provide the specif ic statutory authority for adoption of these regulatory amendments. The Commission also adopted in com pliance with 24-4-103(4) C.R.S. the following statement of basis and purpose.
BASIS AND PURPOSE:
A. Waterbody Segmentation
Some renumbering and/or creation of new segments was made to facilitate appropriate organization of w aterbodies in this regulation. Renumbering and/or creation of new segments was made based on informa tion that showed: a) the original reason for segmentation no longer applied; b) differences in water quality; and/or c) certain segments could be merged into one segment because they had similar water quality an d uses. The following changes were made:
Upper South Platte River segments 11b and 12: Description of segment 12 expanded to include a portion of Bear Creek formerly in segment 11b to allow for Class 1 protection of Bear Creek.
Upper South Platte River segments 16c and 16k: Lakewood Gulch was removed from segment 16c and moved to new segment 16k to allow for Class 1 protection of Lakewood Gulch.
Cherry Creek segments 4a and 4b: This segment was split into segments 4a and 4b to allow for adoption of ambient based, site specific standards for selenium on segment 4b.
Clear Creek segments 7a and 7b: Segment 7 was split into segments 7a and 7b to separate lakes and st reams.
Clear Creek segments 12a and 12b: This segment was split into segments 12a and 12b to allow for Clas s 1 protection of segment 12b.
Boulder Creek segments 1 and 4a: Description of segment 1 was expanded to include the tributaries and wetlands within the James Peak Wilderness Area which had been in segment 4a.
Boulder Creek segments 13 and 15: Description of lakes segment 13 was expanded to include the lakes within the James Peak Wilderness Area which had been in segment 15.
Boulder Creek segment 15: Gross Reservoir was removed from segment 15 and moved to new segment 18 to allow for Class 1 protection of Gross Reservoir.
Cache la Poudre River segments 10a and 10b: Segment 10 was split at the Larimer County Ditch to allo w for Class 1 protection of the portion upstream of the Larimer County Ditch, which is now in new segmen t 10a. The remaining portion downstream of the Larimer County Ditch was moved to new segment 10b a nd remained Class 2.
Republican River segments 1, 2 and 8: Segment 2 was deleted and the lakes and reservoirs in this segm ent were moved to a new segment 9 at the end of the subbasin. This change was reflected in segment 8, which referenced segment 2 and now references segment 9. Bonny Reservoir was removed from the se gment 1 description, as recent evidence indicates that the reservoir no longer holds water and is now man aged as a state wildlife area.
Segment descriptions were also edited to improve clarity, correct typographical errors, and correct spellin g errors. These changes are listed in Section S:
12 B. Revised Aquatic Life Use Classifications and Standards
Some segments were assigned an Aquatic Life use classification, but were missing one standard to prote ct that use. The Commission adopted the missing standards for the following segments:
Upper South Platte River segment: 2c (Cd ac) Clear Creek segments: 11 (Cd trout), 17a and 17b (Ag ch trout) Boulder Creek segments: 4d (Fe) and 5 (Fe) Big Thompson River segment: 18 (DO)
The Commission reviewed information regarding the existing aquatic communities. Class 2 segments wit h high MMI scores or a wide variety of fish species were upgraded from Class 2 to Class 1.
The following segments were upgraded from Cold 2 to Cold 1:
Big Thompson River segment: 4a Boulder Creek segment: 18 (Gross Reservoir) Cache la Poudre River segments: 7 and 10a
The following segments were upgraded from Warm 2 to Warm 1:
Big Thompson River segment: 4b Cache la Poudre River segments: 11 and 12 Republican River segment: 5
The Commission reviewed all Class 2 segments that have fish that are “of a catchable size and which are normally consumed and where there is evidence that fishing takes places on a recurring basis.” Water + f ish or fish ingestion standards were applied to the following segments:
Warm Class 2:
Upper South Platte River segment: 16i Cherry Creek segment: 6 Clear Creek segment: 14b Boulder Creek segment: 17 St. Vrain Creek segment: 12 Middle South Platte River segments: 1a, 1b, 3a and 4 Big Thompson River segments: 13 and 17 Lower South Platte River segment: 1
C. Recreation Classifications and Standards
The Commission reviewed information regarding the current Recreation use classifications and evidence pertaining to actual or potential primary contact recreation. In addition, newly created segments were giv en the same Recreation use classification as the segment from which they were split, unless there was in sufficient evidence to support keeping that classification, or evidence to show that the existing use classifi cation was inappropriate.
Based upon evidence that portions of these segments are publicly accessible and/or accessible to familie s who live in the area or visitors to public recreation lands in these segments, it was determined that there is the potential for primary contact recreation, including water play by children. The following segments wit h year-round or seasonal Recreation N standards were upgraded to Recreation P:
Lower South Platte River segment: 2a Republican River segment: 6
13 Based upon evidence that portions of these segments are publicly accessible and located in a developed area where there is easy access for children, it was determined that primary contact recreation is expecte d to occur. The following segments with year-round or seasonal Recreation N standards were upgraded t o Recreation E:
Clear Creek segments: 16b, 17a and 18b
The following segments with year-round or seasonal Recreation U standards were upgraded to Recreatio n P:
Lower South Platte River segment: 4
D. Water Supply Use Classification and Standards
The Commission added a Water Supply use classification and standards where the evidence demonstrat ed a reasonable potential for a hydrological connection between surface water and alluvial wells used for drinking water. The Water Supply use classification and standards were added to the following segments:
Upper South Platte River segments: 7, 11a, and 16j Cherry Creek segments: 4a and 4b Clear Creek segment: 5 Boulder Creek segments: 7a and 7b Middle South Platte River segments: 3a and 5a Big Thompson River segments: 4b and 9 Lower South Platte River segments: 2a and 3
A review of the segments with an existing Water Supply use classification showed that some segments w ere missing one or more standards to protect that use. The full suite of Water Supply standards was add ed to the following segments:
Cherry Creek segment: 5 St. Vrain Creek segment: 5 Big Thompson River segments: 17 and 19 Cache la Poudre segment: 21 Lower South Platte River segments: 4 and 5 Republican River segment: 8
Three segments have one or more numeric standards for water supply, but do not have the Water Supply use classification. The Division searched for alluvial wells on these segments and determined that there i s not an existing Water Supply use. Therefore, the Water Supply standards were removed from the follo wing segments:
Clear Creek segment: 13b Boulder Creek segment: 8 St. Vrain Creek segment: 6
E. Agriculture Use Classification and Standards
A review of the segments with an existing Agriculture use classification showed that some segments were missing one or more standards to protect that use. The full suite of Agriculture standards were added to t he following segments:
Clear Creek segments: 13b, 16b, 22 and 25 Big Dry Creek segments: 1 and 3
14 Molybdenum: In 2010, the Commission adopted a new standard for molybdenum to protect cattle from th e effects of molybdenosis. The table value adopted at that time was 300 µg/l, but included an assumption of 48 mg/day of copper supplementation to ameliorate the effects of molybdenosis. State and local expert s on cattle nutrition indicated that copper supplementation in the region is common, but is not universal. T herefore, the copper supplementation assumption was removed from the equation, which then yielded a s tandard of 160 µg/l. That standard was applied in recent basin reviews.
In this hearing, the Commission adopted a standard of 150 µg/L, based on an improved understanding of the dietary- and water-intake rates for various life-stages of cattle. This standard is protective of all life-st ages of cattle (including lactating cows and growing heifers, steers and bulls) at all times of year.
The Agriculture table value assumes that the safe copper:molybdenum ratio is 4:1. Food and water intak e is based on growing heifers, steers, and bulls consuming 6.7 kg/day of dry matter and 56.8 liters of wate r per day. Total copper and molybdenum intakes are calculated from the following equations:
Cu intake mg/day = [([Cu] forage, mg/kg) x (forage intake, kg/day)] + [([Cu] water, mg/l) x (water i ntake, L/day)] + (Cu supplementation, mg/day)
Mo intake mg/day = [([Mo] forage, mg/kg) x (forage intake, kg/day)] + [([Mo] water, mg/l) x (water i ntake, L/day)] + (Mo supplementation, mg/day)
The assumed values for these equations are as follows:
[Cu] forage = 7 mg/kg, [Mo] forage = 0.5 mg/kg, forage intake = 6.7 kg/day, [Cu] water = 0.008 m g/L, [Mo] water = 0.375 mg/L, water intake = 56.8 L/day, Cu supplementation = 0 mg/day, Mo sup plementation = 0 mg/day.
A molybdenum standard of 150 µg/l was adopted for all segments in Regulation 38 that have an Agricultu re use classification, and where livestock or irrigated forage are present or expected to be present. The f ollowing segments do not have an Agriculture or a Water Supply use classification. No molybdenum stan dard was applied to these segments:
Clear Creek segments: 7a, 7b and 8
The following segments (or portions of segments) have an Agriculture use classification and a Water Sup ply use, but livestock or irrigated forage are not expected to be present. A molybdenum standard of 210 µg/l was applied to these segments:
Upper South Platte River segment: 22a (McLellan Reservoir) Clear Creek segments: 4 and 5
Grazing of cattle has recently occurred near Segment 5 (West Clear Creek) on the Buckland property (Gu anella Ranch) just west of Empire, CO. However, only limited access exists for cattle to reach West Clear Creek, and discussions between Climax and the property owners have resulted in an agreement to elimin ate access and fence cattle out of the creek prior to any future grazing. Because of this agreement, no liv estock use of the Segment 5 is expected to occur in the future.
The following segments have an Agriculture use classification and no Water Supply use, but livestock or ir rigated forage are not expected to be present. No molybdenum standard was applied to these segments:
Upper South Platte River segment: 16g Clear Creek segment: 25
F. Changes to Antidegradation Designation
15 The Commission reviewed all Warm 2 segments designated Use Protected to determine if the Use Protec ted designation was still warranted. Based upon available water quality data that meet the criteria of 31.8 (2)b, the Use Protected designation was removed from the following segment:
Cache la Poudre River segment: 13a
The Commission reviewed all Warm 1 segments designated Use Protected to determine if the Use Protec ted designation was still warranted. Based upon available water quality data that meet the criteria of 31.8 (2)b, the Use Protected designation was removed from the following segment:
Boulder Creek segment: 7a
The Commission reviewed all Reviewable segments to determine if this Antidegradation designation was still warranted. Based upon available water quality data that fails to meet the criteria of 31.8(2)b, the Revi ewable designation was removed and replaced with Use Protection in the following segment:
St. Vrain Creek segment: 4a
The following segments with Outstanding Waters designations were expanded to include the James Peak Wilderness Area:
Boulder Creek segments: 1 and 13
G. Ambient Standards
Ambient standards are adopted where natural or irreversible man-induced conditions result in exceedanc es of table value standards. The Commission reviewed the information that is the basis for these standar ds, as well as any new information that would indicate whether they are still appropriate, need to be modifi ed, or should be removed.
New ambient-based standards were adopted for the following segments:
Cherry Creek segment 4b: Cottonwood Water and Sanitation District (CWSD) presented evidence in the form of a use attainability analysis (UAA) that the natural and irreversible human-induced ambient seleniu m concentrations in specific portions of Cottonwood Creek, upper Lone Tree Creek and middle Windmill Creek exceed the relevant table value standard. The UAA established that the highest attainable use in t hese reaches includes a low rate of fish deformity due to the naturally elevated levels of selenium. The C ommission created a new Cherry Creek Segment 4b, defined as “Cottonwood Creek, including all tributari es and wetlands, from the source to Cherry Creek Reservoir” to facilitate the adoption of site-specific amb ient-based selenium standards for specific portions of this small watershed, which are adequate to protect the classified, attainable use.
The Commission specified assessment locations at 38.6(4)(i) to ensure that the sites with water quality cu rrently equal to or better than table value standards are protected. Multiple assessment locations are app ropriate because the selenium concentrations decline abruptly and attain TVS standards in the lower reac hes of Lone Tree, Cottonwood and Windmill Creeks. These assessment locations act as demarcation of t he only portions where the elevated selenium levels are allowable. Where selenium levels are currently n aturally elevated, concentrations are significantly higher during the winter months (October through Febru ary) and therefore seasonal standards were adopted to recognize the natural seasonal variation of seleni um concentrations. While data to characterize summer selenium concentrations were limited on Windmill Creek, seasonal ambient standards were adopted based on evidence of a consistent seasonal selenium pattern observed in adjacent drainages.
It is the Commission’s intent that the current natural in-channel processes (e.g., wetlands, infiltration) that remove the selenium are protected, with the intent that lower Cottonwood, Windmill, and Lone Tree Creek
16 s (as defined in the assessment locations) continue to remain in attainment of TVS. The Commission not es that these natural processes that reduce selenium are currently maintained at very low flows. When i mplementing these standards, the Division shall assure that downstream uses and standards are protecte d. Evidence within the UAA was limited to selenium and therefore use classifications, anti-degradation de signation, and water quality standards from parent segment 4 were applied to new segment 4b.
Although the Commission determined that adoption of the ambient-based selenium standard proposed by CWSD and the Division is appropriate, the Commission believes, without intending to establish or limit per mit conditions, that follow-up biological monitoring is warranted to inform future review of the selenium sta ndards. The Commission would expect the collection of additional baseline (“before”) fish tissue selenium data in the Cottonwood Creek watershed below CWSD’s intended point of discharge, and in Cherry Cree k Reservoir. In addition, after the R.O. plant is re-started, the Commission would expect CWSD to collect fish tissue data to support a “before and after” evaluation of downstream effects in the tributaries and rese rvoir. The sampling should focus on the time of year when sensitive species and species that are high sel enium-accumulators are expected to be gravid. This data will be used to evaluate whether the ambient-b ased standard is protective of the use. The Commission expects CWSD to develop a study plan in agree ment with WQCD, CPW, EPA, CCBWQA and other interested parties.
Clear Creek segment 5: The Commission adopted water supply manganese standards representative o f existing quality as of January 1, 2000 with assessment locations provided at 38.6(4)(j). The aquatic life manganese standards still apply throughout the segment.
H. Numeric Standards Changes
Changes were made to the following metals criteria to implement revisions adopted by the Commission in the 2010 Basic Standards rulemaking hearing.
Aluminum: Chronic aluminum standards adopted in 2010 are pH-dependent. When the pH is greater th an 7.0, the new chronic aluminum standard uses a hardness-based equation. When pH is less than 7.0, t he old chronic criterion of 87 µg/l or the new hardness-based equation applies, whichever is more stringe nt. The new acute aluminum criterion is a hardness-based equation that applies at all pH values. The ha rdness for both the chronic and acute aluminum hardness-based equations is capped at 220 mg CaCO3/l, rather than the typical cap of 400 mg CaCO3/l. The acute and chronic aluminum equations in 38.6(3) wer e modified to conform to Regulation No. 31.
Ammonia: Footnote 4 was replaced. The equations for the “NH3=TVS” were deleted and replaced by lan guage that explains the early life stage presence/absence assumptions.
Molybdenum: In 2010, the Commission adopted a new molybdenum standard of 210 µg/L to protect the Water Supply use.
Uranium: The Commission revised the uranium standard in 2010. The new standard is a hyphenated sta ndard with two values (16.8 – 30 µg/L). The first value, which was added in 2010, is a strictly human heal th-based standard. The second value, which was the old standard, is EPA’s maximum contaminant level (MCL), which is higher because it takes into account treatability and detection limits. A new section 38.5 (3)(c)(i) was added to explain the hyphenated standard. Subsection 38.5(3)(d) was deleted because it wa s redundant with 38.5(3)(c).
Zinc: The Commission adopted revisions to the zinc equation in 2010. The new chronic zinc equation is slightly more stringent at hardness values less than 157 mg CaCO3/l. The new acute zinc equation is sligh tly less stringent at all hardness values. The zinc(sculpin) equation was not adopted in Regulation No. 38 because sculpin are not expected in the South Platte River basin. The acute and chronic zinc equations i n 38.6(3) were modified to conform to Regulation No. 31.
I. Numeric Standards: Biotic Ligand-Based Site-Specific Copper Standards
17 In the present hearing, the Commission adopted site-specific copper standards based on the Fixed Monit oring Benchmark (FMB) application of the Biotic Ligand Model (BLM). The Commission recognized that i mplementation guidance is still evolving, but was persuaded that the FMB will now yield criterion-based v alues that better reflect the toxicity of copper than is possible with the hardness-based TVS or WER-base d values. However, there are some important considerations for the acquisition of input data and for the i nterpretation of output values that warrant attention in future proposals.
The Commission envisions applying the BLM primarily downstream of dischargers where concerns about effluent copper may legitimately be offset to some degree by ligands in the effluent that affect the toxicity of copper. Because the potential “benefit” of these ligands is very much dependent on the mix of effluent with the receiving stream, it is important for the model inputs to provide adequate representation of seaso nal and hydrologic variability. Similarly, because water quality conditions change downstream, especially where there are significant hydrologic features (e.g., tributaries and other discharges), it is important to ha ve multiple sites to represent spatial variability and assure downstream protection of uses.
To facilitate future review of the standards adopted in this hearing, the Commission expects proponents to commit to a “longevity plan” with continued monitoring and analysis of BLM parameters culminating in a r eview at the next basin hearing.
In this hearing, FMB-based copper standards were proposed for four segments in which standards previo usly had been WER-based:
Upper South Platte River segments 14, 15, and 16g Middle South Platte River segment 01a.
In addition, the Commission revisited a proposal for Big Thompson segment 2 that received tentative appr oval at the temporary modifications hearing in December, 2014.
Upper South Platte Segment 15 and Middle South Platte Segment 1a, Below Metro
The Metro Wastewater Reclamation District (Metro) has provided a data set and accompanying analysis t hat the Commission has determined can be used as a model for future proposals. The multi-year data col lection effort included biweekly sampling of all parameters required for the BLM at nine sites, providing co mplete spatial coverage of the two segments of interest (US15 and MS01a). Comparison of the FMB valu es across the sites facilitates the selection of one value that is protective in each segment. Addition of co nfidence intervals shows that the most protective values in each segment are not significantly different; he nce, one value can be applied to both segments.
The application of confidence intervals enables future review of the standards adopted in this hearing. Th e Commission recognizes that the water quality conditions prevailing today may be changed in the future i f water management practices or wastewater treatment processes or flows change in the future. Insofar a s the FMB is sensitive to parameters like pH or dissolved organic carbon that could change in the future, it is important to review the new standards regularly. Confidence intervals provide a basis for meaningful c omparison of new and old determinations of the FMB at the same location.
Metro has agreed to continue all necessary data collection and evaluation activities to support review of th e BLM-derived copper standards at the next Regulation No. 38 hearing.
Upper South Platte Segments 14 and 16g, Below Centennial W&SD
Centennial W&SD also applied the BLM to develop a proposal for copper standards. Although the spatial coverage of sites in the initial proposal was very limited, the Division added BLM results from six additiona l sites in rebuttal. The expanded spatial coverage provided a mutually acceptable proposal for Segment 1 4 and assured the Commission that the standard would be protective of the affected portion of that segme nt. The Commission will review these FMB-based standards in the next Basin Review Hearing, using dat
18 a collected over the next five years, to ensure that FMB-based standards capture any changes in water q uality. Centennial has agreed to continue all necessary data collection and evaluation activities to support review of the BLM-derived copper standards at the next Regulation No. 38 hearing
Big Thompson Segment 2, Below Upper Thompson Sanitation District
The modeling that was done to support the Commission’s action in December 2014 was reviewed in light of the experience gained from work in this hearing with the BLM and FMB. The Commission found that th e decisions made in the earlier hearing were consistent with the current work and supported by data and analysis.
Cherry Creek Segment 1, Below Parker Water and Sanitation District
Parker Water and Sanitation District (Parker) presented effluent data indicating that they have a predicted compliance problem with permit limits based on the copper hardness equation on Cherry Creek segment 1. Parker has initiated sampling for parameters required to use the BLM to derive a site-specific standard for copper. Robust derivation of site specific copper standards using the BLM requires temporal coverage of at least 2 years of monthly sampling at sites representative of the segment under consideration. As of t his hearing, Parker did not have sufficient temporal coverage to use the model. Additionally, information presented in Parker’s prehearing statements highlighted recent and future plant process changes which may influence the representativeness of recent sampling. Parker has agreed to continue sampling for 24 months following the last planned operational changes so a more representative dataset can be utilized to derive a site-specific standard for copper with confidence. Given the uncertainty about the appropriate un derlying standard, and the predicted compliance problem, the Commission approved a temporary modific ation for copper set to “current conditions” with an expiration date of 12/31/2020.
J. Numeric Standards: Site-Specific Mercury Standard
The Commission adopted a site-specific total mercury standard of 0.026 µg/L as a chronic, 30-day averag e standard with a 1-in-3 year exceedance frequency on a portion of Upper South Platte Segment 16i, fro m Brighton Boulevard to the confluence with the South Platte River. The table value standard of 0.01 µg/L remains the standard for this segment upstream of Brighton Boulevard.
Suncor collected total mercury fish tissue data and unfiltered water samples for total mercury and methyl mercury analysis from two sites on Sand Creek between Brighton Boulevard and the Burlington Ditch. Su ncor targeted the highest trophic level species in Sand Creek for mercury sampling and collected skinless filets from the largest individuals of each species to analyze for wet-weight total mercury.
Fish tissue bioaccumulation factors (BAFs) were calculated, in part, following EPA’s 2010 Guidance for I mplementing the January 2001 Methylmercury Water Quality Criterion. The calculations also follow reco mmendations from a 2013 study (Riva-Murray et al.) conducted by the U.S. Geological Survey (USGS) an d the U.S. EPA National Exposure Research Laboratory to optimize stream water mercury sampling for th e purpose of developing mercury fish tissue BAFs. The site-specific standard was derived using the follo wing equations:
Site-specific BAF (L/kg) = [arithmetic mean mercury fish tissue concentration in mg/kg wet weight] / [85th p ercentile methylmercury water concentration in mg/L]
Methylmercury water quality criterion (µg/L) = 10-9 x [0.3 mg/kg fish tissue] /[site-specific BAF (L/kg)]
Total mercury water quality criterion (µg/L) = methylmercury criterion * median ratio of total Hg:MeHg
A site-specific BAF was calculated for each species. The methylmercury water quality criterion was calcul ated using only the species with the highest BAF (Lepomis cyanellus, green sunfish) rather than a weight ed average of all larger species. While the green sunfish are less than five inches in length and unlikely t
19 o be consumed, this ensures that the site-specific standard will prevent average fish tissue concentration s from exceeding 0.3 mg/kg for all species. The median ratio of total mercury to methylmercury was calcul ated in order to translate the protective methylmercury water column value to a total mercury water colum n standard. Although methylmercury is the form of mercury that bioaccumulates, the standard is based u pon total mercury, because mercury can change forms in the environment.
Existing quality for this chronic standard is defined as the 85th percentile for permitting and assessment pu rposes. Attainment of the standard shall be assessed by comparing the weighted 85th percentile total mer cury concentration from both assessment locations at 38.6(4)(f) to the site-specific criterion.
Fish tissue concentrations in the South Platte River are expected to be protected despite the increase in t he site-specific standard on Sand Creek. This is due to the low concentrations of mercury previously foun d in fish flesh in the South Platte River during a time when the mercury concentrations from Sand Creek w ere much higher. When the relatively small volume of water in Sand Creek and higher mercury concentra tions are combined with the greater volume of water in the South Platte River and low ambient water colu mn concentrations, the change in concentration downstream of the confluence is negligible. Based on pe rmitted low flow conditions, the projected mercury concentrations in the South Platte River would attain th e existing 0.01 µg/L standard even when mercury concentrations in Sand Creek were as high as 0.053 µg /L (approximately two times the adopted standard in segment 16i).
K. Temporary Modifications
All existing Temporary Modifications were examined to determine if they should be allowed to expire or if t hey should be extended, either unchanged or with changes to the numeric limits. Temporary modification of copper standards for Cherry Creek segment 1 is discussed above (section I). Temporary modification t emperature standards are discussed below in section M.
The Commission deleted or allowed to expire on 12/31/2015 certain temporary modifications on the follow ing segments:
Upper South Platte River segments: 14, 15, 16g and 16i Clear Creek segments: 9a, 11, 14a, 14b and 15 Boulder Creek segment: 9 St. Vrain Creek segments: 2b and 6 Middle South Platte River segments: 1a and 4 Big Thompson River segments: 2 and 5 Cache la Poudre River segments: 11 and 12 Lower South Platte River segment: 1
The Commission revised or extended Temporary Modification on the following segments:
Bear Creek segment: 1c Clear Creek segment: 2c, 13b Boulder Creek segment: 8 Big Thompson River segments: 4b and 9 Cache la Poudre River segment: 13b
To remain consistent with the Commission’s decisions regarding arsenic in section 38.85, all existing tem porary modifications for arsenic of “As(ch)=hybrid” (expiration date of 12/31/21) were retained. An arseni c temporary modification was added to the following segments, which had an existing or newly added chr onic arsenic standard 0.02 µg/L and a permitted discharger with a water quality–based effluent limit compl iance problem:
Upper South Platte River segments: 2c and 22a Bear Creek segments: 1b, 4a, 5, 6b and 11
20 Clear Creek segment: 5, 9a, 11 and 14b Boulder Creek segments: 3, 4b and 7a St. Vrain Creek segments: 2b and 7 Middle South Platte River segments: 1a, 3a and 4 Big Thompson River segments: 3, 4a and 4b Cache la Poudre River segment: 10b Lower South Platte River segment: 1
The Commission adopted Temporary Modifications on the following segments:
Upper South Platte River segments: 10a, 14 and 15 Cherry Creek segment: 1 Clear Creek segments: 2c, 7a, 7b and 11 Boulder Creek segment: 9
Upper South Platte segment 10a: The Commission adopted a temporary modification for manganese i n segment 10a of the Upper South Platte River. PCWRA presented information that shows a demonstrat ed water quality based effluent compliance problem. The Commission reviewed the temporary modificati on implementation plan submitted by PCWRA. Based on that plan, along with the compliance problem an d uncertainty regarding the standard, the Commission adopted a “Current Conditions” temporary modifica tion to the manganese standard in Upper South Platte segment 10a with an expiration date of 6/30/2019.
Upper South Platte segment 14: The Commission adopted a temporary modification for chloride in seg ment 14 of the Upper South Platte River. Centennial presented information that shows a predicted water quality based effluent limit compliance problem. The Commission reviewed the temporary modification im plementation plan submitted by Centennial. Based on that plan, along with the compliance problem and u ncertainty regarding the standard the Commission adopted a “Current Conditions” temporary modification to the chloride standard in Upper South Platte segment 14 with an expiration date of 12/31/2020.
Upper South Platte segment 15: The Commission adopted a temporary modification for chloride and su lfate in Segment 15 of the Upper South Platte River. Public Service Company presented information that shows a predicted water quality based effluent limit compliance problem. The Commission reviewed the t emporary modification implementation plan submitted by Public Service Company. Based on that plan, al ong with the compliance problems and uncertainty regarding the standards the Commission adopted a “C urrent Conditions” temporary modification to the chloride and sulfate standards in Upper South Platte seg ment 15 with an expiration date of 12/31/2020.
Clear Creek segment 2c: The Commission adopted a new temporary modification for cadmium and rev ised the temporary modification for copper both with an expiration date of 7/01/2020. Evidence submitted by the CCCSD identifies that it would continue to have a permit compliance problem if ambient quality wa s implemented in its discharge permit. During the effective period of this temporary modification, copper and cadmium limits for existing dischargers to Segment 2c will be authorized to continue based on past fa cility performance (existing effluent quality) unless a more stringent limitation is reasonably achievable wit hout requiring significant investment in facility infrastructure, consistent with Regulation 31.14(16).
Big Thompson segment 9: Little Thompson River, Big Thompson Segment 9: The Division’s noticed pr oposal for this segment originally included a “current conditions” temporary modification as a result of the basin wide practice of extending selenium temporary modifications on segments that continue to indicate i mpairment. The Town of Milliken presented evidence of a compliance problem with the permit limits base d on the underlying selenium table value standard as well as evidence that elevated selenium levels origi nate from naturally occurring, selenium rich shale and also proposed the same changes. In order to ensur e that the current condition in segment 9 is protected over the duration of the temporary modification, the Division changed its proposal to reflect existing quality in the form of a numeric temporary modification. A mbient selenium conditions at a long term monitoring site above the outfall indicate the 85th percentile of s elenium concentrations equal 12.3 µg/l. Therefore, the Commission extended the expiration date of the te mporary modification to 12/31/2020 and changed the numeric value in the temporary modification for sele
21 nium from 13.1 µg/l to 12.3 µg/l to reflect the addition of more recent data. It is the Commission’s intent th at no assimilative capacity is created through this action.
The Town of Milliken has volunteered to complete a phased plan to evaluate potential selenium impacts t o fish populations within the segment. Milliken will develop a detailed sampling and analysis plan for the fi rst phase in coordination with a qualified consultant and CPW by 7/15/2015. Sampling will commence as soon as technically practicable in 2015 and will first focus on fish tissue selenium analysis of ovaries/eggs of larger female fish, and muscle or whole body analysis for other fish. Milliken’s commitment to follow-up phases is contingent on Milliken’s continued intent to utilize their existing surface water discharge permit. I f necessary, and after coordination between CDPHE, Milliken, and CPW, a second phase of the study will be to evaluate larval fish deformity rates and/or selenium bioaccumulation through the foodchain. Results of this analysis will be presented at a future Temporary Modifications Rulemaking Hearing in 2018 or 201 9 or before. If the results demonstrate that uses are protected, an ambient-based site-specific standard m ay be appropriate.
L. Temperature Standards
The Commission adopted new criteria for temperature in 2007. In June 2009, segment-specific temperat ure standards were adopted by the Commission for all segments with an Aquatic Life use classification in the South Platte River basin.
In June 2010, revisions of the temperature criteria in Regulation No. 31 resulted in changes to warm strea m temperature tiers. The expected range of the razorback sucker is also habitat for the more thermally se nsitive white sucker. Because the temperature tier applied to a segment is based on the most thermally s ensitive species, the razorback sucker tier had never been applied. Therefore, the Commission deleted t he razorback sucker tier (warm stream tier III), and included the razorback sucker in warm stream tier II. I n implementation of these changes, the Commission changed all warm stream tier IV segments to warm s tream tier III to conform with the 2010 revisions, which affected the following segments:
Upper South Platte River segments: 16d, 16e and 16f Middle South Platte River segments: 3b, 5b and 6 Republican River segment: 7
In 2010, the Commission also reformatted the temperature criteria in 31.16 Table I and updated the value s based on new data included in the Colorado Temperature Database. Several corrections were made to the temperature criteria. Both the Arctic grayling and golden shiner were moved from stream tiers to the c old and warm lake tiers, respectively, because both species are found only in lakes. Additionally, a typogr aphical error in the chronic temperature criterion for cold stream tier II and large lakes and reservoirs was corrected.
Changes were made to bring Regulation No. 38 into conformity with all of the 2010 revisions to the Basic Standards for temperature, including updating the temperature tables at 38.6(3).
Based upon new information on the species expected to occur, the Commission changed the temperature standard from CS-II to CS-I for the following segments:
Clear Creek segment: 12b
Ambient temperature standards for lakes
In the 2009 triennial review, the WAT standard was found to be unattainable for a number of cold large la kes and reservoirs with apparently healthy cold-water fish populations. Because summertime temperatur e in the mixed layer for large lakes and reservoirs is very well correlated to the waterbody’s elevation, the Commission adopted ambient temperature standards for large lakes wherever data were available to char
22 acterize a WAT and the thermal characteristics of the lakes and reservoirs were determined to be the res ult of natural or irreversible man-induced conditions.
However, the 2010 revisions to the dissolved oxygen criteria in Regulation No. 31 altered how lakes and r eservoirs are assessed for temperature and dissolved oxygen. The Commission decided that dissolved o xygen may be less than the applicable standard in the lower portion of a lake or reservoir except where R egulation No. 31 footnote 5(c)(iii) applies or a site-specific standard has been adopted.
Footnote 5(c)(iii) states:
When a lake or reservoir is stratified, the mixed layer may exceed the criteria in Table 1 provided that an adequate refuge exists in water below the mixed layer. Adequate refuge depends on conc urrent attainment of applicable dissolved oxygen standards. If the refuge is not adequate because of dissolved oxygen levels, the lake or reservoir may be included on the 303(d) List as “impaired” for dissolved oxygen, rather than for temperature.
Therefore, the ambient standards adopted by the Commission in 2009, which were based solely on the W AT and did not account for the concept of refuge, may no longer be appropriate or protective of the aquati c life use. To ensure that adequate refuge is defined in a way that protects the Aquatic Life use, the Com mission adopted Footnote D which was applied to the temperature standard for deep stratified lakes. Foo tnote D states “Assessment of adequate refuge shall rely on the Cold Large Lake table value temperature criterion and applicable dissolved oxygen standard rather than the site-specific temperature standard”, an d was applied to following lake segments:
Upper South Platte River segment: 19 (Eleven Mile Reservoir) Boulder Creek segment: 18 (Gross Reservoir) Big Thompson River segment: 11 (Carter Lake) Cache la Poudre River segment: 14 (Horsetooth Reservoir)
M. Temperature Temporary Modifications
At the basin hearing in 2009 and in subsequent hearings, concerns have been registered about the imple mentation of temperature standards. In particular, major POTWs discharging to streams with an Aquatic Life Warm classification have expressed reservations about the technical basis for winter standards and c oncerns about compliance prospects.
These concerns have occupied much of the Commission’s time at this hearing and are likely to do so agai n at the Basic Standards hearing next year. Although the issues cannot be resolved completely today, th e Commission has taken two actions that will provide some guidance for future actions. The first is to ado pt temporary modifications in a way that acknowledges compliance problems common to most discharger s to warm streams, and the second is to comment on what has been learned about resolving temperature problems.
Temporary modifications have been adopted for all segments with an Aquatic Life Warm classification wh ere a discharger has shown a compliance problem. The temporary modifications are restricted for most s egments, to the winter season (December-February). The exception is for Cache la Poudre segment 12, where the Commission decided, for reasons explained below, that it was appropriate to adopt a temporar y modification for the full year rather than just the winter months. Year-round temporary modifications wer e also adopted for Upper South Platte segment 15 and Clear Creek segments 11, 14a, 14b, and 15, wher e work is underway on discharger specific variance proposals. Most of these temporary modifications will be in effect through 12/31/2020, which is synchronized with the next South Platte basin hearing.
The Commission is aware that not all parties are satisfied with temporary modifications at this time. In par ticular, Littleton/Englewood put considerable effort into development of a site-specific proposal that was n
23 ot adopted. Consequently, it may be helpful for the Commission to comment again on possible approach es to resolving temperature issues.
At the last South Platte basin hearing in 2009 (see 38.74(M)), temporary modifications and site-specific standards were adopted in some of the same segments that were considered at the present hearing. Spe cifically with respect to Upper South Platte segments 14, 15, and 16g, the Commission stated its expectati on that “domestic wastewater facilities will, in cooperation with other dischargers and the Division, explore options for developing new underlying site-specific temperature standards including refined numeric site-s pecific standards, ambient–based site-specific standard and narrative site-specific standards although per mit implementation strategies are not yet fully developed for all of these.” In addition, the Commission co mmented on a “facility-specific variance approach … [that] may be an appropriate solution….” It is appar ent now that the facilities in question have worked largely independently and have relied on different appr oaches.
In the years following adoption of temperature criteria, interested parties have amassed temperature data from many segments in the South Platte basin. The extensive records of spatial and temporal temperatur e patterns have done much to inform the Commission about the influence of POTW discharges on stream temperature. In warm streams, a large discharge can increase stream temperature as much as 10 degre es C in the winter, but may cause relatively little change in the summer. This potential compliance proble m occurs primarily in the winter months.
The options for addressing temperature issues remain essentially the same now as they were in 2009, ex cept that the “facility-specific variance” (now the DSV) is officially available. What has changed is that the re is now a more complete appreciation of the level of difficulty for developing a successful proposal. Dev elopment of a site-specific standard (criterion or ambient; numeric or narrative) is a challenging undertakin g that is hampered by the paucity of scientific information regarding wintertime thermal requirements of w arm water fish communities. The challenge is compounded by having to determine which species are ex pected to occur in the fish community. These are not new difficulties and they will continue to confront fut ure efforts.
The record in this hearing included expressions of concerns about the implementation of temperature sta ndards, the feasibility of meeting temperature standards, and the scientific basis for the warm-water winte r temperature standards. These concerns involve multiple aspects of the State’s clean water program, inc luding standards, permitting, and engineering. The Commission supports the use of Division resources a cross multiple units to address uncertainties about the temperature standards and their implementation.
From the Commission’s perspective, it is important to see a showing that a proposed change to a temper ature standard will protect the use. The bar for demonstrating protectiveness of temperature standards w as set high in previous hearings and documents, and it has not changed. In adopting changes to tempera ture regulations in 2007 (see 31.45), the Commission broadened provisions protecting spawning to “ensur e that the thermal requirements for successful migration, spawning, egg incubation, fry rearing and other r eproductive functions are met”. The Commission specifically linked winter criteria to protection of reprodu ctive functions.
While the Commission understands that the absence of formal guidance may make the development of a standard more difficult, it does not absolve the proponent of the responsibility to show that the proposed s tandard will meet the intent of the regulation. Proposals submitted to date have encountered stiff challeng es from the Division, EPA and CPW largely on the question of protectiveness. The alternative to developi ng a new use-based standard, which was suggested as early as 2007, would be to seek a variance (DSV). A DSV, perhaps sector-based, would provide the foundation for reasonable incremental progress to redu ce winter heat load to streams without imposing an unachievable compliance schedule.
1. Warm Stream Temporary Modifications:
Littleton/Englewood (L/E), South Platte segment 14: L/E has proposed relaxing the temperatu re standards in December and February in Segment 14. The proposal is based largely on field st
24 udies and relies on this evidence to show that one of the temperature-sensitive species – the Joh nny darter – is not suffering adverse effects from increased winter temperatures downstream of th e outfall. The proposal failed because there was no showing that the proposed standards would be protective, specifically, L/E has not demonstrated that the proposed standards would protect al l life stages including reproduction and early life stages. Field studies are generally insufficient be cause the effects of confounding factors are not addressed adequately. Site-specific criteria are generally based on controlled studies in the laboratory.
Instead, the Commission accepts the Division’s proposal that a temporary modification is appropri ate at this time. It affords L/E, and other parties with similar issues, the opportunity to work togeth er to find a path forward either in the Basic Standards hearing proceedings or through the collecti ve work that is now proceeding on the feasibility of treatment (cooling) options.
PCWRA, Centennial, Boulder, Ft Collins, multiple segments: Plum Creek Water Reclamation Authority (Upper South Platte segment 10a) Centennial (Upper South Platte segments 16g and 1 4), Boulder (Boulder Creek segment 9, and Fort Collins (Cache La Poudre segment 11) all propo sed solutions for winter temperature effluent limit compliance problems. The Commission agrees that there are concerns about compliance with temperature limits that are common to several part ies to this hearing. In Warm streams, dischargers are likely to experience compliance problems i n the winter (Dec-Feb). Winter is also the season in which thermal requirements are poorly know n for species expected to occur in Warm streams. The combination of compliance problems and uncertainty about the underlying standards is a necessary condition for a temporary modification.
It is the Commission’s hope that workgroup efforts prior to the Basic Standards hearing will help r esolve uncertainty about the winter temperature standards. However, even if a better technical b asis emerges from that hearing, there is no guarantee that it will resolve all of the compliance pro blems expected by many of the dischargers. Consequently, the Commission encourages all parti es to consider what progress can be made regarding the scope of an alternatives analysis that mi ght support a DSV.
Greeley, Cache la Poudre segment 12: The standards in this segment affect several discharge rs, two of which participated in the present hearing. Consequently, the Commission lacks a comp lete picture of temperature patterns and potential problems. The City of Greeley, which discharge s near the downstream end of Segment 12, predicts compliance problems in the summer, but not in the winter. The compliance problems may be associated in part with times when ambient temp eratures exceed the standard.
Temperature data on the record are not adequate to determine if ambient temperatures are eleva ted throughout Segment 12 or only at the downstream end. The City of Fort Collins submitted dat a for a site at the downstream end of adjacent Segment 11, which does not show the same attain ment problem. There is uncertainty about the underlying standard in Segment 12, and resolution of that uncertainty likely will affect other dischargers (e.g., Windsor and Carestream). Resolution, if it results in an ambient standard for all or part of Segment 12, may also reduce the likelihood of compliance problems for Greeley.
Greeley has adequate justification for a temporary modification in the summer, but has no compli ance problem in the winter. Regarding the potential for compliance problems in the winter, the C ommission believes that the evidence from other segments, including Cache La Poudre Segment 11, is sufficiently compelling to justify a temporary modification for the winter months. Permit limit s for the discharger at the downstream end of Segment 11 (Ft Collins Drake) may be affected by proximity to Segment 12. In addition, the Windsor and Carestream facilities would seem likely to have winter compliance problems, although the evidence is not currently on the record.
Metro, Upper South Platte segment 15: In this hearing the Commission extended the expiration date for the temperature temporary modification on Upper South Platte segment 15. The tempor ary modification, set at current conditions, will expire on 12/31/2020. The Metro District will contin
25 ue to refine a temperature discharger-specific variance proposal for the Robert W. Hite Treatment Facility with input from the Division, Colorado Parks and Wildlife, U.S. EPA Region 8, and South Adams County Water and Sanitation District for future consideration by the Commission.
MillerCoors, Clear Creek segments 11, 14a, 14b, 15: The Commission extended the “current c onditions” temporary modifications for temperature until June 30, 2019 for Segments 14a, 14b an d 15 and adopted a new temporary modification for temperature on Segment 11 from a point imm ediately downstream of the 6th Avenue Bridge to the Farmers Highline Canal diversion, also with a June 30, 2019 expiration date. MillerCoors has shown that there is uncertainty about whether a discharger-specific variance may be appropriate and will complete an alternatives analysis with in put from the Division, U.S. EPA Region 8 and other interested stakeholders to address the uncert ainty.
2. Cold Stream Temporary Modifications:
Black Hawk Central City, Clear Creek segment 13b: The Commission extended the expiration date for the temperature temporary modification for Segment 13b. The temporary modification, se t at current condition, will now expire on December 31, 2020. BHCCSD and Black Hawk provided temperature data demonstrating a predicted compliance issue year-round. In addition, there rema ins uncertainty regarding the appropriate temperature standard for Segment 13b; while aquatic lif e is currently limited by poor water quality and habitat, water quality conditions are expected to im prove. The EPA and Colorado Hazardous Materials Waste Management Division plan to constru ct a water treatment plant in the upper portion of Segment 13b that will remove metals from the G regory Incline, Gregory Gulch ground water, and the National Tunnel; extension of the temporary modification will allow time for BHCCSD and Black Hawk to evaluate the effects of improved wate r quality on aquatic life in Segment 13b following water treatment plant construction and determin e the appropriate temperature standards for Segment 13b.
BHCCSD and Black Hawk submitted an outline of a plan to collect additional temperature data fro m existing sites and other sites in Segment 13b to better characterize the longitudinal temperatur e variability of the stream. During the summer of 2015, BHCCSD and Black Hawk will also condu ct side by side temperature measurements in the stream to verify the accuracy of temperature me asurements that have been collected to-date. BHCCSD and Black Hawk also plan to review wate r quality data collected by UCCWA. BHCCSD and Black Hawk will continue to collect benthic ma croinvertebrate data and will coordinate with CPW to collect additional fish population data to bett er characterize the species and life stages expected to be present in Segment 13b. Additionally, BHCCSD and Black Hawk initiated a discussion with UCCWA at its May 2015 meeting regarding riparian restoration potential within Segment 13b, and will continue the dialogue during the period of the temporary modification. An UCCWA agenda item will be scheduled for the fall of 2015. BH CCSD and Black Hawk will also evaluate whether a discharger specific variance would be consist ent with 31.7(4). The Commission expects that BHCCSD and Black Hawk will work with the Divis ion and CPW to develop the detailed plan within the next year. At the December 2018 temporary modification review hearing, the Commission will consider extending the duration of the temporar y modification if more time is needed to evaluate the recovery of the aquatic life community and d etermine the appropriate temperature standards, or if other delays occur, particularly related to co nstruction of the water treatment plant
Climax, Clear Creek segments 7a and 7b: The Commission adopted a new temporary modific ation of the temperature standard for these segments of “current conditions” for the months of Oct ober, November, April, and May. The Commission recognizes that there is uncertainty about the appropriate temperature standard because of recent channel improvements done by Climax Moly bdenum Company in Woods Creek between Upper Urad Reservoir and Lower Urad Reservoir in 2012-2015. It is uncertain whether and how the channel improvements will affect in-stream tempe ratures or whether sensitive life stages of cold water fish will be expected to be present in the sho rt reach of restored surface channel downstream of the Henderson water treatment facility outfall on Woods Creek.
26 The Commission adopted the temporary modifications with an expiration date of June 30, 2023. Climax will delay site-specific studies in Woods Creek, to allow Climax to complete construction a nd establish operational practices for water management and control of the new channels, and ev aluate conditions in the channels including possible establishment of aquatic life in the channels. Conditions may change once the new channel stabilizes; therefore, an extended temporary modifi cation duration is appropriate. The Commission will review progress on the study plan at the 2019 Issues Formulation Hearing for the South Platte Basin.
N. Nutrients
In March 2012, the Commission adopted interim nutrient values in the Basic Standards (Regulation No. 3 1) and created a new statewide control regulation (Regulation No. 85) to address nutrients in Colorado. R egulation 31.17 includes interim nutrient values for total phosphorus, total nitrogen, and chlorophyll a for b oth lakes and reservoirs, and rivers and streams. Due to the phased implementation approach adopted w ith these criteria (31.17(e)), the Commission adopted only total phosphorus and chlorophyll a standards at this time. Nitrogen standards were not considered as part of this rulemaking hearing, but will be consider ed in the next triennial review, currently scheduled for June 2020.
Total phosphorus and chlorophyll a standards were adopted for waters upstream of all permitted domestic wastewater treatment facilities discharging prior to May 31, 2012 or with preliminary effluent limits request ed prior to May 31, 2012, and any non-domestic facilities subject to Regulation No. 85 effluent limits and d ischarging prior to May 31, 2012. A new section (4) was added at 38.5 describing implementation of the i nterim nutrient values into the tables at 38.6, and includes a table which lists these facilities and the segm ent to which they discharge.
For segments located entirely above these facilities, nutrient standards apply to the entire segme nt.
For segments with portions downstream of these facilities, nutrient standards only apply above th ese facilities. A footnote “C” was added to the total phosphorus and chlorophyll a standards in the se segments. The footnote references the table of qualified facilities at 38.5(4).
For segments located entirely below these facilities, nutrient standards do not apply.
For rivers and streams segments, total phosphorus standards were adopted for segments with an aquatic life use. Chlorophyll a standards were adopted for segments with either an E or P recreation use classific ation.
For lakes and reservoirs segments, a Footnote B was added to total phosphorus and chlorophyll standard s adopted for lakes in the tables at 38.6, as these standards only apply to lakes larger than 25 acres.
31.17(e)(iii) also allows the Commission to adopt numeric nutrient standards for Direct Use Water Supply (DUWS) lakes and reservoirs. No proposals were made to adopt standards based on this provision in thi s rulemaking (see section O).
31.17(e)(iii) also allows the Commission to adopt numeric nutrient standards for circumstances where the provisions of Regulation No. 85 are not adequate to protect waters from existing or potential nutrient pollu tion. No proposals were made to adopt standards based on this provision in this rulemaking.
Chlorophyll a standards were adopted for the following segments:
Upper South Platte River segments: 1a, 1b, 2a, 2c, 3, 4, 5a, 5b, 7, 8, 9, 10a, 11a, 11b, 12, 13, 16 c, 16d, 16f, 16h, 16i, 16j, 16k,18 and 19 Cherry Creek segments: 1, 4a, 4b and 5 Bear Creek segments: 1a, 3, 5, 6a, 7, 8 and 9
27 Clear Creek segments: 1, 2a, 2b, 2c, 3a, 3b, 4, 5, 6, 9a, 9b, 10, 13a, 13b, 16a, 16b, 17a, 17b, 18 a, 18b, 19, 20, 21, 22 and 24 Boulder Creek segments: 1, 2a, 2b, 3, 4a, 4b, 4c, 4d, 6, 7a, 8, 13, 14, 15 and 18 St. Vrain Creek segments: 1, 2a, 2b, 4a, 4b, 4c, 5 and 10 Middle South Platte River segments: 3a and 3b Big Thompson River segments: 1, 2, 6, 7, 8, 9 and 10 Cache la Poudre River segments: 1, 2a, 2b, 6, 8, 9, 13a, 13b, 13c, 16, 18, 19, 20 and 21 Laramie River segments: 2a, 3 and 4 Lower South Platte River segments: 2a, 2b, 3, 4 and 5 Republican River segments: 3, 4, 5, 6 and 9
Total Phosphorus standards were adopted for the following segments:
Upper South Platte River segments: 1a, 1b, 2a, 2c, 3, 4, 5a, 5b, 7, 8, 9, 10a, 11a, 11b, 12, 13, 16 c, 16d, 16f, 16h, 16i, 16j, 16k, 18 and 19 Cherry Creek segments: 1, 4a, 4b and 5 Bear Creek segments: 1a, 3, 5, 6a, 7, 8, and 9 Clear Creek segments: 1, 2a, 2b, 2c, 3a, 3b, 4, 5, 6, 7a, 9a, 9b, 10, 12, 13a, 13b, 16a, 16b, 17a, 7b, 18a, 18b, 19, 20, 21, 22, 23, 24 and 25 Boulder Creek segments: 1, 2a, 2b, 3, 4a, 4b, 4c, 4d, 6, 7a, 8, 13, 14, 15 and 18 St. Vrain Creek segments: 1, 2a, 2b, 4a, 4b, 4c, 5 and 10 Middle South Platte River segments: 3a, 3b, 5a, 5c and 6 Big Thompson River segments: 1, 2, 6, 7, 8, 9 and 10 Cache la Poudre River segments: 1, 2a, 2b, 6, 8, 9, 13a, 13b, 13c, 16, 18, 19, 20 and 21 Laramie River segments: 2a, 3 and 4 Lower South Platte River segments: 2a, 2b, 3, 4 and 5 Republican River segments: 3, 4, 5, 6, 7 and 9
Big Dry Creek Segment 1: Total phosphorus and chlorophyll-a standards do not apply to the mainstem of Big Dry Creek downstream of Standley Lake, because Standley Lake is filled by ditches that withdraw wat er downstream of multiple permitted domestic wastewater treatment facilities.
1. Site-Specific Total Phosphorus Standards
The Commission continues to support a phased implementation approach to adoption of nutrient criteria. However, it is also clear from evidence on the record that some segments merit special c onsideration. The Cherry Creek Basin Water Quality Authority (CCBWQA) submitted data in its r esponsive statement showing that background phosphorus levels exceed TVS. The Division con curs with this finding, which also has been documented in previous hearings related to Watershed Control Regulation No. 72. A background concentration has been established to support estimati on of phosphorus loads to Cherry Creek Reservoir, but it is not yet known if that concentration sh ould be applied uniformly as a stream standard throughout the basin.
A similar situation, albeit with less supporting evidence, has been identified by the Bear Creek Wa tershed Association (BCWA) in Bear Creek Segment 7. In this case, the evidence suggests that f en wetlands have background phosphorus levels that exceed TVS even though streams in the sa me segment do not have elevated phosphorus levels. It is not yet known what background level would be appropriate or if it varies among the fens.
The Commission applauds the efforts of CCBWQA and BCWA to obtain, and make available for t his hearing, data that improve our understanding of existing conditions within each basin. Site-s pecific standards are needed for all, or part, of the segments for which phosphorus standards hav e been proposed, but there is uncertainty about the habitat type or the geographic scope of applic ability for site-specific standards (or conversely for the TVS). Resolving the uncertainty will requir e additional sampling to obtain representative data. A temporary modification cannot be used to provide the additional time because adoption of the phosphorus standard, as proposed in this hea
28 ring, would not result in a compliance problem for a discharger. However, delaying the effective d ate by five years would give CCBWQA, BCWA, and/or any other interested party or parties time t o collect additional data and propose site-specific phosphorus standards as appropriate.
Total Phosphorus standards were given a delayed effective date of 12/31/2020 in the following se gments:
Cherry Creek Segments 1, 4a and 4b Bear Creek Segment 7 (wetland fens)
2. Bear Creek Reservoir Total Phosphorus and Chlorophyll a Standards
The site-specific standards for chlorophyll a and total phosphorus have been revised in response to US E PA’s disapproval of the Commission’s 2009 action. The purpose for the revised standards remains consi stent with the Commission’s original goal of shifting the trophic condition to the mesotrophic-eutrophic bou ndary. The numeric values for chlorophyll and phosphorus have changed because the data set has been expanded by several years and an improved methodology has been applied. As before, the standards w ere developed using only data from Bear Creek Reservoir. Each standard is defined for average summer concentrations and has an allowable exceedance frequency of once in five years.
A. Chlorophyll Standard: The Commission revised the chlorophyll standard to 12.2 μg/L. If summer average chlorophyll concentrations in the reservoir exceed 12.2 µg/L more than once in five years, it would be firm evidence that the trophic condition goal of the pre- existing narrative (mesotrophic-eutrophic boundary) was not being met. The exceedance threshold of 12.2 µg/L was derived with a “translator” developed with data from Bear Creek Reservoir. The translator connects the concentration at the allowable exceedance frequency (once in five years) to the typical concentration at the mesotrophic-eutrophic boundary (8 μg/L).
B. Phosphorus Standard: The Commission revised the phosphorus standard to 22.2 μg/L. The standard is calculated in two steps based on the methodology used to develop statewide nutrient criteria for the 2012 Nutrient hearing. The first step involves the creation of a statistical “linkage” between phosphorus and chlorophyll based on summer average concentrations measured in Bear Creek Reservoir. The linkage is used to define the phosphorus concentration corresponding to the mesotrophic-eutrophic boundary in this reservoir; that concentration is 16 µg/L. The second step involves a translator for phosphorus that performs the same function described for the chlorophyll translator described above. The concentration at the exceedance threshold is 22.2 µg/L.
C. Assessment: The phosphorus and chlorophyll standards are defined as seasonal averages. Samples are to be collected at a site in deep water near the dam and should be representative of conditions in the mixed layer. Past monitoring has resulted in 5 or 6 samples during the summer months (July, August, and September); it is anticipated that the same level of effort will be applied in the future. For assessment, the average (arithmetic mean) is calculated for the summer samples in each year.
D. Independent Applicability: The chlorophyll and phosphorus standards are considered independently applicable. That is, impairment can be determined with either parameter without confirmation by the other parameter. Although the parameters are linked biologically – algae require phosphorus to grow – the linkage is “noisy” in a statistical sense because phosphorus cannot compel algae to grow (i.e., other limiting factors complicate the relationship). Independent applicability establishes a more sensitive basis for assessing departures from the target trophic condition since regulation of phosphorus cannot be used to guarantee attainment of the chlorophyll standard. Independent applicability is a practical way to adapt regulation to a complex natural relationship where neither constituent is toxic (at least not at the target levels).
29 E. Adoption of a Temporary Modification for Chlorophyll and Phosphorus: The underlying standards are not attained presently due to the seasonal augmentation of phosphorus concentrations from internal sources. A temporary modification set at “current conditions” to expire 12/31/2020, is adopted in order to recognize the uncertainty regarding how soon the internal load will be reduced. The Division, in conjunction with the Bear Creek Watershed Association, is working on studies to determine what management strategies might be feasible for reducing or controlling internal phosphorus release. Progress on resolving uncertainty will be reviewed in the annual temporary modification hearings in December 2018 and 2019.
O. Direct Use Water Supply Sub-classification
Also in the March 2012 rulemaking hearing, the Commission adopted a sub-classification of the Domestic Water Supply Use called “Direct Use Water Supply Lakes and Reservoirs Sub-classification” (Regulation 31, at 31.13(1)(d)(i)). This sub-classification is for Water Supply lakes and reservoirs where there is a pla nt intake location in the lake or reservoir or a man-made conveyance from the lake or reservoir that is use d regularly to provide raw water directly to a water treatment plant that treats and disinfects raw water. Th e Commission has begun to apply this sub-classification and anticipates that it will take several basin revi ews to evaluate all the reservoirs in the basin. The Commission adopted the DUWS sub-classification on the following reservoirs and added “DUWS” to the classification column in the standards tables. The publi c water systems are listed along with the reservoirs and segments.
Upper South Platte River segment 16b: Aurora Reservoir (City of Aurora)
Upper South Platte River segment 19: Strontia Springs Reservoir (Denver Water Board)
Upper South Platte River segment 21: Aurora Rampart Reservoir (City of Aurora)
Upper South Platte River segment 22a: McLellan Reservoir (Centennial W&SD), Quincy Reserv oir (City of Aurora)
Bear Creek segment 1d: Evergreen Lake (Evergreen Metro District)
Clear Creek segment 17a: Arvada Reservoir (City of Arvada)
Clear Creek segment 23: Ralston Reservoir (Denver Water Board, City of Arvada, North T able Mtn W&S)
Clear Creek segment 24: Maple Grove Reservoir (Cons Mutual/Maple Grove)
Big Dry Creek segment 2: Standley Lake (City of Northglenn, City of Thornton, City of West minster)
Boulder Creek segment 14: Lakewood Reservoir (City of Boulder)
Boulder Creek segment 15: Kossler Lake (City of Boulder)
Boulder Creek segment 17: Baseline Reservoir (City of Lafayette), Marshall Lake (City of Lou isville), Thomas Reservoir (Town of Erie) and Waneka Reservoir (City of Lafayette)
St. Vrain Creek segment 7: Boulder Reservoir (City of Boulder) Spurgeon (Lefthand WD,Niw ot)and Left Hand Valley Reservoir (Lefthand WD,Niwot)
St. Vrain Creek segment 10: Joder Reservoir (Lefthand WD,Niwot)
30 St. Vrain Creek segment 13: Burch Lake (City of Longmont)
Big Thompson River segment 11: Carter Lake (City of Louisville)
Big Thompson River segment 12: Boyd and Loveland Lakes (City of Greeley)
Big Thompson River segment 13: Berthoud (Town of Berthoud) and Johnstown Reservoir (Town of Johnstown)
Big Thompson River segment 14: Lonetree Reservoir (Town of Johnstown)
Big Thompson River segment 16: St. Mary’s Lake (Prospect Mtn)
Cache la Poudre River segment 14: Horsetooth Reservoir (City of Ft. Collins, Soldier Canyon FP, Spring Canyon W&SD, City of Greeley, Platte River Power Authority)
Cache la Poudre River segment 21: North Poudre Reservoir No. 3 (Town of Wellington)
31.17(e)(iii) also allows the Commission to adopt numeric nutrient standards for Direct Use Water Supply (“DUWS”) lakes and reservoirs. No standards were adopted based on this provision in this rulemaking.
P. Chromium III Standards
A review of the chromium III standards showed that uses were not always adequately protected by the sta ndards currently in the tables. For example, the acute Aquatic Life standard is not protective of Water Su pply at any hardness, so the Water Supply standard of CrIII(ac)=50(Trec) was added to all segments with a Water Supply use. Additionally, the chronic standard to protect the Aquatic Life use classification may n ot be protective of the Agriculture use in some high-hardness situations. Therefore, a chromium III standa rd of CrIII(ch)=100(Trec) was added to segments with Aquatic Life and Agriculture use classifications, but no Water Supply use. At hardness less than 145 mg/L, the Agriculture standard is not protective of the A quatic Life use, so the chronic chromium III Aquatic Life standard should be included/retained in all segme nts with an Aquatic Life use.
Uses Acute Chronic Water supply CrIII(ac) = 50(Trec) CrIII(ch) = TVS (with or without Agriculture) CrIII(ch) = TVS No water supply CrIII(ac) = TVS and (with Agriculture) CrIII(ch) = 100(Trec) Aquatic Life Only CrIII(ac) = TVS CrIII(ch) = TVS (without Water Supply or Agriculture)
The Commission updated chronic chromium III standards to be consistent with the matrix for the following segments:
Upper South Platte River segments: 1a, 1b, 2b, 2c, 5c, 5d, 6a, 6b, 7, 8, 10a, 11a, 11b, 12, 13, 14, 15, 16a, 16b, 16c, 16d, 16e, 16f, 16g, 16h, 16i, 16j, 17a, 17b, 17c, 18, 19, 20, 21, 22a, 22b and 2 3
Cherry Creek segments: 1, 2, 3, 4a, 4b, 5 and 6
Bear Creek segments: 1c, 2, 4a, 5, 6a, 6b, 10, 11 and 12
31 Clear Creek segments: 2a, 2b, 2c, 4, 5, 9b, 11, 12, 13b, 14a, 14b, 15, 16a, 16b, 17a, 18a, 18b, 1 9, 21, 22, 23, 24 and 25
Big Dry Creek segments: 1, 2, 3, 4a, 4b, 5, 6 and 7
Boulder Creek segments: 4a, 4b, 4c, 4d, 5, 6, 7a, 7b, 8, 9, 10, 11, 13, 14, 15, 16 and 17
St. Vrain Creek segments: 3, 4a, 4b, 4c, 6, 7, 8, 9, 10, 11 and 13
Big Thompson River segments: 3, 4a, 4b, 4c, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18 and 19
Middle South Platte River segment: 3a, 3b, 5a, 5b, 5c and 7
Cache la Poudre River segments: 7, 8, 9, 10a, 10b, 11, 12, 13b, 13c, 14, 15, 16, 17, 18, 19, 20, 21 and 22
Laramie River segments: 1, 2a, 2b, 3 and 4
Lower South Platte River segments: 2a, 2b, 3, 4 and 5
Republican River segments: 1, 3, 4, 5, 8 and 9
Q. Other Standards for the Protection of Agriculture and Water Supply Uses
Similar to the issue identified in Section P above, there were additional segments where one or more use s are not adequately protected by current standards. For instance, depending on hardness, the Aquatic L ife standards for cadmium, lead, and nickel were not protective of the Water Supply use. The Division rev iewed all segments in Regulation No. 38 to determine if the current standards applied to each segment ar e fully protective of the assigned uses, and revised or added standards where appropriate.
A cadmium Water Supply standard was added to the following segments because the acute Aquatic Life standard is not protective when the hardness was greater than 200 mg/L in non-trout streams and 345 mg /L in trout streams. A lead Water Supply standard was added to the following segments because the acut e Aquatic Life standard is not protective when hardness is greater than 79 mg/L. A nickel Water Supply st andard was added to the following segments because the chronic Aquatic Life standard is not protective when hardness is greater than 216 mg/L. Cadmium, lead, and nickel Water Supply standards were adde d to the following segments:
Upper South Platte River segments: 1a, 1b, 2a, 2b, 2c, 3, 4, 5b, 5c, 5d, 6a, 6b, 7, 8, 9, 10a, 11a, 12, 13, 14, 15, 16b, 16i, 16j, 18, 19, 20, 21 and 22a Cherry Creek segments: 1, 2, 3, 4a, 4b and 5 Bear Creek segments: 1a, 1b, 1c, 1d, 1e, 2, 3, 4a, 5, 6a, 6b, 7, 8, 9, 10, 11 and 12 Clear Creek segments: 1, 2a, 2b, 2c, 3a, 3b, 4, 5, 6, 9a, 9b, 10, 11, 12, 13a, 14a, 14b, 15, 16a, 1 7a, 17b, 18a, 18b, 19, 20, 21, 23 and 24 Big Dry Creek segments: 2, 4a, 4b, 5, 6 and 7 Boulder Creek segments: 1, 2a, 2b, 3, 4a, 4b, 4c, 4d, 5, 6, 9, 10, 11, 13, 14, 15, 16 and 17 St. Vrain Creek segments: 1, 2a, 2b, 4a, 4b, 4c, 5, 7, 8, 9, 10, 11, 12 and 13 Middle South Platte River segments: 1a, 1b, 4 and 7 Big Thompson River segments: 1, 2, 3, 4a, 4b, 7, 8, 11, 12, 13, 14, 15, 16, 17, 18 and 19 Cache la Poudre River segments: 1, 2a, 2b, 6, 7, 8, 9, 10a, 10b, 13a, 13c, 14, 15, 17, 18, 19, 20 and 21 Laramie River segments: 1, 2a, 2b, 3 and 4 Lower South Platte River: 1, 2a, 3, 4 and 5 Republican River: 1, 3, 5, 8 and 9
32 R. Other Site-Specific Revisions
Marston Forebay: Section 25-8-101(19), C.R.S., and Rule 31.5(38) of Regulation 38 defines “State Water s” as excluding “all water withdrawn for use until use and treatment have been completed.” The Commiss ion finds and determines for the following reasons that water contained within Marston Forebay meets this exclusion. Marston is an off-channel forebay, fed through Denver Water’s Conduit 20, which diverts water from the South Platte River, and Conduit 15, which diverts water from Bear Creek. Water withdrawn from these two man-made conveyances is held in Marston until treated at the adjacent Marston Water Treatme nt Plant and used within Denver Water’s potable water distribution system. Marston Forebay is located o n a topographical rise and therefore has no surface water influence, other than precipitation. In addition, t here is no infiltration of groundwater into the Forebay, and the amount of infiltration from the Forebay to gr oundwater is de minimis and inconsistent. The Forebay is surrounded by four dams and a dike, and four o perational toe-drain systems that capture and manage seepage from the Forebay. There is also no mana ged fishery at Marston Forebay, and public access to the Forebay is restricted. The Commission created a new section 38.7 “Commission’s Determinations Regarding State Waters” an listed Marston Forebay in this new section. In addition, a qualifier pointing at 38.7 was added to Upper South Platte segment23.
Clear Creek segments 7a and 7b: The Commission adopted Table Value Standards for Woods Creek an d Lower Urad Reservoir for the protection of aquatic life. The Commission recognizes that there is uncerta inty about the appropriate metals standards because of recent channel improvements done by Climax Mo lybdenum Company in Woods Creek between Upper Urad Reservoir and Lower Urad Reservoir in 2012 t o 2015. It is uncertain whether and how the channel improvements will affect metals or whether sensitive l ife stages of cold water fish will be expected to be present in the short reach of restored surface channel d ownstream of the Henderson water treatment facility on Woods Creek. The Commission adopted tempor ary modifications for cadmium, copper, iron, lead, mercury, nickel, silver and zinc with an expiration date of 6/30/2023. (The temperature temporary modification is discussed above in section M.)
The Commission adopted the temporary modifications with an expiration date of June 30, 2023. Climax wi ll delay site-specific studies in Woods Creek, to allow Climax to complete construction and establish oper ational practices for water management and control of the new channels, and evaluate conditions in the c hannels including possible establishment of aquatic life in the channels. Conditions may change once the new channel stabilizes; therefore, an extended temporary modification duration is appropriate. The Comm ission will review progress on the study plan at the 2019 Issues Formulation Hearing for the South Platte Basin.
Clear Creek segments 14a, 14b, and 15: An expiration date of 12/31/2020 was added to all segments with a site-specific standard based upon water effect ratios. These standards are derived by measuring the toxicity of a pollutant to test organisms in laboratory water compared with the receiving water, including effluent. Changes in water chemistry, such as hardness, alkalinity and the concentrations of other toxics can all impact the toxicity of a specific pollutant, such as zinc. If there are significant changes in the chemistry of the receiving water or the effluent, then the water effect ratio analysis must be repeated and the site-specific standard updated to reflect current conditions. Since the water effect ratio studies for these segments were completed in the 1990s, the Commission applied an expiration date to require re-evaluation of these standards at the next triennial review.
Big Dry Creek segment 1, assessment locations: A site-specific standard for selenium for Big Dry Creek S egment 1 was adopted in 2007. In this hearing, the Commission replaced the assessment location bdc4. 0 with bdc4.5 to provide safer access for field staff collecting samples. Bdc4.5 is located approximately on e-half mile downstream of bdc4.0. Bdc4.5 represents instream conditions upstream of the City of Northgl enn’s discharge, which was the original purpose of sampling location bdc4.0. Attainment of the selenium s tandard will be assessed based on data collected at bdc1.5, bdc2.0 and bdc4.5. Data collected at the form er site bdc4.0 may continue to be used for assessment. A typographical correction was also made for sam pling location bdc2.0.
S. Typographical and Other Errors
33 The following edits were made to improve clarity and correct typographical errors:
• For Upper South Platte segments 9 and 20, “a.k.a. Waucondah Reservoir” was added to clarify the location of the waterbody.
• For Upper South Platte segment 10a, the second “Temporary Modification” was deleted and the expiration date was moved to a new line for clarity and consistency
• For Upper South Platte segment 12, a space was added to “Class1”.
• For Upper South Platte segment 16a, the selenium standards were split over two lines (i.e., Se(ac)=TVS and Se(ch)=TVS). The Division combined these (i.e., Se(ac/ch)=TVS) to be consistent with formatting elsewhere. Similarly, for Clear Creek Segment 2b, the Division combined the Zn(ac)=TVS and Zn(ch)=TVS into Zn(ac/ch)=TVS. For Clear Creek Segment 16a, the Division combined the Cd(ac)=TVS and Cd(ch)=TVS into Cd(ac/ch)=TVS.
• For Upper South Platte segments 16h, 16i, and 16j, the Division standardized the formatting of the site-specific selenium standards to be consistent among segments.
• For Upper South Platte segment 21, the Division corrected the chronic arsenic standard, which was missing a digit (i.e., “0.02-0(Trec)” was replaced with “0.02-10(Trec)”).
• For Upper South Platte segment 22b and St. Vrain Creek Segment 6, the Division corrected the chronic arsenic standard by adding “(Trec)”, consistent with formatting elsewhere.
• For Bear Creek segments 1c, 1d, 1e, 2, and 3, the “equals” sign was missing from the chronic iron standard for water supply. The Division corrected this typo.
• For Bear Creek segment 1c, the temporary modifications were reformatted for consistency.
• For Bear Creek segment 9, specific naming of Summit Lake was included to increase clarity.
• For Bear Creek segment 11, there was an extra space in the segment description. The Division corrected this typo.
• For Clear Creek segments 4, 5, 6, 7a, 8, the stream name was corrected as “West” Fork Clear Creek.
• For Clear Creek segment 9a, the typo “the” was removed.
• For Clear Creek segments 12 and 23, the Division corrected a formatting issue in the metals column.
• For Clear Creek segment 13a, punctuation was corrected.
• For Clear Creek segment 13b, the extra space after the word “Gulch” was deleted.
• For Clear Creek segment 21, the extra comma after the word “CO” was deleted.
• For Clear Creek segment 21 and 22, the word “baseline” was capitalized for consistency.
• For Clear Creek segment 24, the space within the word “Segments” was deleted.
• For Clear Creek segment 25, the description was revised to provide a more detailed location description.
34 • For Big Dry Creek segment 4b, the extra period at the end of the description was deleted.
• For Big Dry Creek segment 5, the typo “a” was removed and “for segment 5” was added to complete the note.
• For Boulder Creek segment 1, the segment description was expanded to include James Peak Wilderness Area and “s” was added to “Area”.
• For Boulder Creek segment 2b, the typo “the” was removed.
• For Boulder Creek segment 4a, the segment description was amended to exclude listings in segment 1 for clarity.
• For Boulder Creek segment 13, the segment description was expanded to include James Peak Wilderness Area and “s” was added to “Area”.
• For Boulder Creek segment 14, Lakewood Reservoir was added to the segment description for identification of DUWS.
• For Boulder Creek segment 15, Gross Reservoir was removed from this segment and moved to new segment 18. The description of segment 15 was amended to exclude listings in segment 13 and 18 for clarity.
• For St. Vrain Creek segment 7, Spurgeon Reservoir was added to the segment description for identification of DUWS. Additionally, the “and” between Coot Lake and Left Hand was deleted.
• For Middle South Platte segment 5b, the spelling of “Boxelder” was changed to Box Elder to be consistent with maps.
• For Middle South Platte segment 6, the Division added (ch) to all of the Metals standards to be consistent with formatting elsewhere.
• For Middle South Platte segment 6, the description was clarified by replacing “Lost Creek from Interstate 76 south…” with “Lost Creek from the source to Interstate 76….”
• For Big Thompson segment 16, St. Mary’s Lake was added to the segment description for identification of DUWS.
• For Cache le Poudre segments 2a and 10a, the spelling “Monroe” was changed to “Munroe”, the word “Headgate” was added, and the description was clarified by replacing “/North Poudre Supply canal diversion” with “(also known as the North Poudre Supply Canal diversion)”.
• For Lower South Platte segment 4, both the nitrate and nitrite standards were duplicated in the Inorganic column of the tables. The Division deleted the least restrictive nitrate/nitrite set.
• For Republican River segment 5, the Division deleted an extra “the” from the segment description.
PARTIES TO THE RULEMAKING HEARING
1. Big Dry Creek Watershed Association 2. City of Black Hawk and Black Hawk/Central City Sanitation District 3. City of Boulder 4. Centennial Water and Sanitation District 5. Central Clear Creek Sanitation District
35 6. Climax Molybdenum Company 7. Cottonwood Water and Sanitation District 8. Denver Water 9. City of Fort Collins 10. Front Range Energy 11. City of Greeley 12. Littleton/Englewood Wastewater Treatment Plant 13. Metro Wastewater Reclamation Fistrict 14. MillerCoors 15. Town of Milliken 16. Parker Water and Sanitation District 17. Plum Creek Water Reclamation Authority 18. Public Service Company of Colorado 19. Suncor Energy (U.S.A.) Inc 20. City of Northglenn 21. Colorado Parks and Wildlife 22. City of Westminster 23. Bear Creek Watershed Association 24. Upper Clear Creek Watershed Association 25. City of Golden 26. U.S. Environmental Protection Agency 27. South Adams County Water and Sanitation District 28. Colorado Trout Unlimited 29. City and County of Broomfield 30. City and County of Denver 31. Chatfield Watershed Authority 32. Town of Castle Rock 33. Douglas County Public Works 34. Cherry Creek Basin Water Quality Authority
36